doc: man-page for the sound command

Provide a man-page for the sound command.

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

doc/usage/cmd/sound.rst

@@ -0,0 +1,41 @@
+.. SPDX-License-Identifier: GPL-2.0+
+.. Copyright 2022, Heinrich Schuchardt <xypron.glpk@gmx.de>
+
+sound command
+=============
+
+Synopsis
+--------
+
+::
+
+    sound init
+    sound play [len [freq]]
+
+Description
+-----------
+
+The *sound* command is used to play a beep sound.
+
+sound init
+    initializes the sound driver.
+
+sound play
+    plays a square wave sound. It does not depend on previously calling
+    *sound init*.
+
+len
+    duration of the sound in ms, defaults to 1000 ms
+
+freq
+    frequency of the sound in Hz, defaults to 400 Hz
+
+Configuration
+-------------
+
+The sound command is enabled by CONFIG_CMD_SOUND=y.
+
+Return value
+------------
+
+The return value $? is 0 (true) if the command succeeds, 1 (false) otherwise.

doc/usage/index.rst

@@ -73,6 +73,7 @@ Shell commands
    cmd/scp03
    cmd/setexpr
    cmd/size
+   cmd/sound
    cmd/temperature
    cmd/tftpput
    cmd/true