doc: Move the generic memory-documentation to doc/

Move this section of the README into doc/ with some minor updates to
mention SPL and user lower-case hex.

Signed-off-by: Simon Glass <sjg@chromium.org>
Acked-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>

README

@@ -2516,51 +2516,6 @@ On RISC-V, the following registers are used:
 
     ==> U-Boot will use gp to hold a pointer to the global data
 
-Memory Management:
-------------------
-
-U-Boot runs in system state and uses physical addresses, i.e. the
-MMU is not used either for address mapping nor for memory protection.
-
-The available memory is mapped to fixed addresses using the memory
-controller. In this process, a contiguous block is formed for each
-memory type (Flash, SDRAM, SRAM), even when it consists of several
-physical memory banks.
-
-U-Boot is installed in the first 128 kB of the first Flash bank (on
-TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
-booting and sizing and initializing DRAM, the code relocates itself
-to the upper end of DRAM. Immediately below the U-Boot code some
-memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
-configuration setting]. Below that, a structure with global Board
-Info data is placed, followed by the stack (growing downward).
-
-Additionally, some exception handler code is copied to the low 8 kB
-of DRAM (0x00000000 ... 0x00001FFF).
-
-So a typical memory configuration with 16 MB of DRAM could look like
-this:
-
-	0x0000 0000	Exception Vector code
-	      :
-	0x0000 1FFF
-	0x0000 2000	Free for Application Use
-	      :
-	      :
-
-	      :
-	      :
-	0x00FB FF20	Monitor Stack (Growing downward)
-	0x00FB FFAC	Board Info Data and permanent copy of global data
-	0x00FC 0000	Malloc Arena
-	      :
-	0x00FD FFFF
-	0x00FE 0000	RAM Copy of Monitor Code
-	...		eventually: LCD or video framebuffer
-	...		eventually: pRAM (Protected RAM - unchanged by reset)
-	0x00FF FFFF	[End of RAM]
-
-
 System Initialization:
 ----------------------
 

doc/develop/index.rst

@@ -13,6 +13,7 @@ General
    codingstyle
    designprinciples
    docstyle
+   memory
    patman
    process
    release_cycle

doc/develop/memory.rst

+.. SPDX-License-Identifier: GPL-2.0-or-later
+
+Memory Management
+-----------------
+
+.. note::
+
+  This information is outdated and needs to be updated.
+
+U-Boot runs in system state and uses physical addresses, i.e. the
+MMU is not used either for address mapping nor for memory protection.
+
+The available memory is mapped to fixed addresses using the
+memory-controller. In this process, a contiguous block is formed for each
+memory type (Flash, SDRAM, SRAM), even when it consists of several
+physical-memory banks.
+
+U-Boot is installed in XIP flash memory, or may be loaded into a lower region of
+RAM by a secondary program loader (SPL). After
+booting and sizing and initialising DRAM, the code relocates itself
+to the upper end of DRAM. Immediately below the U-Boot code some
+memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN
+configuration setting]. Below that, a structure with global Board-Info
+data is placed, followed by the stack (growing downward).
+
+Additionally, some exception handler code may be copied to the low 8 kB
+of DRAM (0x00000000 ... 0x00001fff).
+
+So a typical memory configuration with 16 MB of DRAM could look like
+this::
+
+	0x0000 0000	Exception Vector code
+	      :
+	0x0000 1fff
+	0x0000 2000	Free for Application Use
+	      :
+	      :
+
+	      :
+	      :
+	0x00fb ff20	Monitor Stack (Growing downward)
+	0x00fb ffac	Board Info Data and permanent copy of global data
+	0x00fc 0000	Malloc Arena
+	      :
+	0x00fd ffff
+	0x00fe 0000	RAM Copy of Monitor Code
+	...		eventually: LCD or video framebuffer
+	...		eventually: pRAM (Protected RAM - unchanged by reset)
+	0x00ff ffff	[End of RAM]