doc: Migrate Process wiki page to Sphinx

Move the current Process wiki page to doc/develop/process.rst.  The
changes here are for formatting or slight rewording so that it reads
well when linking to other Sphinx documents.

Cc: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: Tom Rini <trini@konsulko.com>

doc/develop/index.rst

@@ -11,6 +11,7 @@ General
 
    codingstyle
    designprinciples
+   process
 
 Implementation
 --------------

doc/develop/process.rst

+.. SPDX-License-Identifier: GPL-2.0+:
+
+U-Boot Development Process
+==========================
+
+Management Summary
+------------------
+
+* Development happens in Release Cycles of 3 months.
+
+* The first 2 weeks are called Merge Window, which is followed by a
+  Stabilization Period.
+
+* Patches with new code get only accepted while the Merge Window is open.
+
+* A patch that is generally in good shape and that was submitted while the
+  Merge Window was open is eligible to go into the upcoming release, even if
+  changes and resubmits are needed.
+
+* During the Stabilization Period, only patches that contain bug fixes get
+  applied.
+
+Phases of the Development Process
+---------------------------------
+
+U-Boot development takes place in `Release Cycles
+<https://www.denx.de/wiki/U-Boot/ReleaseCycle>`_.  A Release Cycle lasts
+normally for three months.
+
+The first two weeks of each Release Cycle are called *Merge Window*.
+
+It is followed by a *Stabilization Period*.
+
+The end of a Release Cycle is marked by the release of a new U-Boot version.
+
+Merge Window
+------------
+
+The Merge Window is the period when new patches get submitted
+(and hopefully accepted) for inclusion into U-Boot mainline.
+
+This is the only time when new code (like support for new processors or new
+boards, or other new features or reorganization of code) is accepted.
+
+Twilight Time
+-------------
+
+Usually patches do not get accepted as they are - the peer review that takes
+place will usually require changes and resubmits of the patches before they
+are considered to be ripe for inclusion into mainline.
+
+Also, the review often happens not immediately after a patch was submitted,
+but only when somebody (usually the responsible custodian) finds time to do
+this.
+
+In the result, the final version of such patches gets submitted after the
+merge window has been closed.
+
+It is current practice in U-Boot that such patches are eligible to go into the
+upcoming release.
+
+In the result, the release of the ``"-rc1"`` version does not immediately follow
+the closing of the Merge Window.
+
+Stabilization Period
+--------------------
+
+During the Stabilization Period only patches containing bug fixes get
+applied.
+
+Corner Cases
+------------
+
+Sometimes it is not clear if a patch contains a bug fix or not.
+For example, changes that remove dead code, unused macros etc. or
+that contain Coding Style fixes are not strict bug fixes.
+
+In such situations it is up to the responsible custodian to decide if he
+applies such patches even when the Merge Window is closed.
+
+Exception: at the end of the Stabilization Period only strict bug
+fixes my be applied.
+
+Sometimes patches miss the the Merge Window slightly - say by few
+hours or even a day. Patch acceptance is not as critical as a
+financial transaction, or such. So if there is such a slight delay,
+the custodian is free to turn a blind eye and accept it anyway. The
+idea of the development process is to make it foreseeable,
+but not to slow down development.
+
+It makes more sense if an engineer spends another day on testing and
+cleanup and submits the patch a couple of hours late, instead of
+submitting a green patch which will waste efforts from several people
+during several rounds of review and reposts.
+
+Differences to the Linux Development Process
+--------------------------------------------
+
+* In Linux, top-level maintainers will collect patches in their trees and send
+  pull requests to Linus as soon as the merge window opens.
+  So far, most U-Boot custodians do not work like that; they send pull requests
+  only at (or even after) the end of the merge window.
+
+* In Linux, the closing of the merge window is marked by the release of the
+  next ``"-rc1"``
+  In U-Boot, ``"-rc1"`` will only be released after all (or at least most of
+  the) patches that were submitted during the merge window have been applied.
+
+Custodians
+----------
+
+The Custodians take responsibility for some area of the U-Boot code.  The
+in-tree ``MAINTAINERS`` files list who is reponsible for which areas.
+
+It is their responsibility to pick up patches from the mailing list
+that fall into their responsibility, and to process these.
+
+A very important responsibility of each custodian is to provide
+feedback to the submitter of a patch about what is going on: if the
+patch was accepted, or if it was rejected (which exact list of
+reasons), if it needs to be reworked (with respective review
+comments). Even a "I have no time now, will look into it later"
+message is better than nothing. Also, if there are remarks to a
+patch, these should leave no doubt if they were just comments and the
+patch will be accepted anyway, or if the patch should be
+reworked/resubmitted, or if it was rejected.
+
+Work flow of a Custodian
+------------------------
+
+The normal flow of work in the U-Boot development process will look
+like this:
+
+#. A developer submits a patch via e-mail to the u-boot-users mailing list.
+   U-Boot has adopted the `Linux kernel signoff policy <https://groups.google.com/g/fa.linux.kernel/c/TLJIJVA-I6o?pli=1>`_, so the submitter must
+   include a ``Signed-off-by:`` line.
+
+#. Everybody who can is invited to review and test the changes.  Reviews should
+   reply on the mailing list with ``Acked-by`` lines.
+
+#. The responsible custodian
+
+   #. inspects this patch, especially for:
+
+   #. :doc:`codingstyle`
+
+   #. Basic logic:
+
+      * The patch fixes a real problem.
+
+      * The patch does not introduce new problems, especially it does not break
+        other boards or architectures
+
+   #. U-Boot Philosophy
+
+   #. Applies cleanly to the source tree
+
+   #. passes a ``MAKEALL`` compile test without creating new warnings
+
+#. Notes:
+
+  #. In some cases more than one custodian may be affected or feel responsible.
+     To avoid duplicated efforts, the custodian who starts processing the
+     patch should send a short ACK to the mailing list.
+
+  #. We should create some tool to automatically do this.
+
+  #. This is well documented in :doc:`designprinciples`.
+
+  #. The custodian decides himself how recent the code must be.  It is
+     acceptable to request patches against the last officially released
+     version of U-Boot or newer.  Of course a custodian can also accept
+     patches against older code.
+
+  #. Commits should show original author in the ``author`` field and include all
+      sign off/ack lines.
+
+#. The custodian decides to accept or to reject the patch.
+
+#. If accepted, the custodian adds the patch to his public git repository and
+   notifies the mailing list. This note should include:
+
+   * a short description of the changes
+
+   * the list of the affected boards / architectures etc.
+
+   * suggested tests
+
+   Although the custodian is supposed to perform his own tests
+   it is a well-known and accepted fact that he needs help from
+   other developers who - for example - have access to the required
+   hardware or tool chains.
+   The custodian request help for tests and feedback from
+   specific maintainers and U-Boot users.
+
+#. Once tests are passed, some agreed time limit expires, the custodian
+   requests that the changes in his public git repository be merged into the
+   main tree. If necessary, the custodian may have to adapt his changes to
+   allow for a clean merge.
+   Todo: define a reasonable time limit. 3 weeks?