doc: sandbox: Add docs for the sb command
This command has a few small features, so document it.
Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/doc/usage/cmd/sb.rst b/doc/usage/cmd/sb.rst
new file mode 100644
index 0000000..6f54f9d
--- /dev/null
+++ b/doc/usage/cmd/sb.rst
@@ -0,0 +1,54 @@
+.. SPDX-License-Identifier: GPL-2.0+
+
+.. index::
+ single: sbi (command)
+
+sbi command
+===========
+
+Synopsis
+--------
+
+::
+
+ sb handoff
+ sb state
+
+Description
+-----------
+
+The *sb* command is used to display information about sandbox's internal
+operation. See :doc:`/arch/sandbox/index` for more information.
+
+sb handoff
+~~~~~~~~~~
+
+This shows information about any handoff information received from SPL. If
+U-Boot is started from an SPL build, it shows a valid magic number.
+
+sb state
+~~~~~~~~
+
+This shows basic information about the sandbox state, currently just the
+command-line with which sandbox was started.
+
+Example
+-------
+
+This shows checking for the presence of SPL-handoff information. For this to
+work, ``u-boot-spl`` must be run, with build that enables ``CONFIG_SPL``, such
+as ``sandbox_spl``::
+
+ => sb handoff
+ SPL handoff magic 14f93c7b
+
+This shows output from the *sb state* subcommand::
+
+ => sb state
+ Arguments:
+ /tmp/b/sandbox/u-boot -D
+
+Configuration
+-------------
+
+The *sb handoff* command is only supported if CONFIG_HANDOFF is enabled.
diff --git a/doc/usage/index.rst b/doc/usage/index.rst
index b7c80ef..cb7a23f 100644
--- a/doc/usage/index.rst
+++ b/doc/usage/index.rst
@@ -104,6 +104,7 @@
cmd/reset
cmd/rng
cmd/saves
+ cmd/sb
cmd/sbi
cmd/scmi
cmd/scp03