doc/usage: cmd: documentation for meson/sm command

Added docs for Meson Security Monitor command.

Signed-off-by: Alexey Romanov <avromanov@sberdevices.ru>
Reviewed-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>
Link: https://lore.kernel.org/r/20230110105650.54580-4-avromanov@sberdevices.ru
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>

doc/usage/cmd/sm.rst

@@ -0,0 +1,44 @@
+.. SPDX-License-Identifier: GPL-2.0+:
+
+sm command
+==========
+
+Synopis
+-------
+
+::
+
+    sm serial <address>
+    sm reboot_reason [name]
+    sm efuseread <offset> <size> <address>
+    sm efusewrite <offset> <size> <address>
+    sm efusedump <offset> <size>
+
+Description
+-----------
+
+The sm command is used to request services from the secure monitor. User
+can call secure monitor to request special TEE function, for example chip
+serial number info, reboot reason, etc.
+
+sm serial
+  Retrieve chip unique serial number from sm and write it to memory on
+  appropriate address.
+
+sm reboot_reason
+  Print reboot reason to the console, if parameter [name] isn't specified.
+  If parameter specified, set reboot reason string to environment variable
+  with this name.
+
+sm efuseread
+  Read <size> bytes starting from <offset> from efuse memory bank and write
+  result to the address <address>.
+
+sm efusewrite
+  Write into efuse memory bank, starting from <offset>, the <size> bytes
+  of data, located at address <address>.
+
+Configuration
+-------------
+
+To use the sm command you must specify CONFIG_CMD_MESON=y

doc/usage/index.rst

@@ -74,6 +74,7 @@ Shell commands
    cmd/setexpr
    cmd/size
    cmd/sound
+   cmd/sm
    cmd/temperature
    cmd/tftpput
    cmd/true