doc: loads man-page

Provide a man-page for the loads command.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>

doc/usage/cmd/loads.rst

+.. SPDX-License-Identifier: GPL-2.0+:
+
+loads command
+=============
+
+Synopsis
+--------
+
+::
+
+    loads [offset [baud]]
+
+Description
+-----------
+
+The loads command is used to transfer a file to the device via the serial line
+using the Motorola S-record file format.
+
+offset
+    offset added to the addresses in the S-record file
+
+baud
+    baud rate to use for download. This parameter is only available if
+    CONFIG_SYS_LOADS_BAUD_CHANGE=y
+
+Example
+-------
+
+As example file to be transferred we use a script printing 'hello s-record'.
+Here are the commands to create the S-record file:
+
+.. code-block:: bash
+
+    $ echo 'echo hello s-record' > script.txt
+    $ mkimage -T script -d script.txt script.scr
+    Image Name:
+    Created:      Sun Jun 25 10:35:02 2023
+    Image Type:   PowerPC Linux Script (gzip compressed)
+    Data Size:    28 Bytes = 0.03 KiB = 0.00 MiB
+    Load Address: 00000000
+    Entry Point:  00000000
+    Contents:
+       Image 0: 20 Bytes = 0.02 KiB = 0.00 MiB
+    $ srec_cat script.scr -binary -CRLF -Output script.srec
+    $ echo -e "S9030000FC\r" >> script.srec
+    $ cat script.srec
+    S0220000687474703A2F2F737265636F72642E736F75726365666F7267652E6E65742F1D
+    S1230000270519566D773EB6649815E30000001700000000000000003DE3D97005070601E2
+    S12300200000000000000000000000000000000000000000000000000000000000000000BC
+    S11A00400000000F0000000068656C6C6F20732D7265636F72640A39
+    S5030003F9
+    S9030000FC
+    $
+
+The load address in the first S1 record is 0x0000.
+
+The terminal emulation program picocom is invoked with *cat* as the send
+command to transfer the file.
+
+.. code-block::
+
+    picocom --send-cmd 'cat' --baud 115200 /dev/ttyUSB0
+
+After entering the *loads* command the key sequence <CTRL-A><CTRL-S> is used to
+let picocom prompt for the file name. Picocom invokes the program *cat* for the
+file transfer. The loaded script is executed using the *source* command.
+
+.. code-block::
+
+    => loads $scriptaddr
+    ## Ready for S-Record download ...
+
+    *** file: script.srec
+    $ cat script.srec
+
+    *** exit status: 0 ***
+
+    ## First Load Addr = 0x4FC00000
+    ## Last  Load Addr = 0x4FC0005B
+    ## Total Size      = 0x0000005C = 92 Bytes
+    ## Start Addr      = 0x00000000
+    => source $scriptaddr
+    ## Executing script at 4fc00000
+    hello s-record
+    =>
+
+Configuration
+-------------
+
+The command is only available if CONFIG_CMD_LOADS=y. The parameter to set the
+baud rate is only available if CONFIG_SYS_LOADS_BAUD_CHANGE=y
+
+Return value
+------------
+
+The return value $? is 0 (true) on success, 1 (false) otherwise.

doc/usage/index.rst

@@ -68,6 +68,7 @@ Shell commands
    cmd/load
    cmd/loadb
    cmd/loadm
+   cmd/loads
    cmd/loadx
    cmd/loady
    cmd/mbr