doc: sleep man-page

Provide a man-page for the sleep command.

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

doc/usage/cmd/sleep.rst

@@ -0,0 +1,45 @@
+.. SPDX-License-Identifier: GPL-2.0+
+.. Copyright 2023, Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
+
+sleep command
+=============
+
+Synopsis
+--------
+
+::
+
+    sleep <delay>
+
+Description
+-----------
+
+The *sleep* command waits for *delay* seconds. It can be interrupted by
+CTRL+C.
+
+delay
+   delay in seconds. The value is decimal and can be fractional.
+
+Example
+-------
+
+The current data and time is display before and after sleeping for 3.2
+seconds:
+
+::
+
+    => date; sleep 3.2; date
+    Date: 2023-01-21 (Saturday)    Time: 16:02:41
+    Date: 2023-01-21 (Saturday)    Time: 16:02:44
+    =>
+
+Configuration
+-------------
+
+The command is only available if CONFIG_CMD_SLEEP=y.
+
+Return value
+------------
+
+The return value $? is 0 (true) if the command completes.
+The return value is 1 (false) if the command is interrupted by CTRL+C.

doc/usage/index.rst

@@ -76,6 +76,7 @@ Shell commands
    cmd/scp03
    cmd/setexpr
    cmd/size
+   cmd/sleep
    cmd/sound
    cmd/source
    cmd/temperature