[PATCH v2 1/5] binman: add documentation for binman sign option

[Ivan Mikhaylov <fr0st61te@gmail.com>]

Add the documentation about binman sign option and providing an
example.

Signed-off-by: Ivan Mikhaylov <fr0st61te@gmail.com>
---
 tools/binman/binman.rst | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/tools/binman/binman.rst b/tools/binman/binman.rst
index 0921e31878..c9d352e3ba 100644
--- a/tools/binman/binman.rst
+++ b/tools/binman/binman.rst
@@ -1330,6 +1330,24 @@ You can also replace just a selection of entries::
 
 .. _`BinmanLogging`:
 
+Signing FIT container with private key in an image
+--------------------------------------------------
+
+You can sign FIT container with private key in your image.
+For example::
+
+    $ binman sign -i image.bin -k privatekey -a sha256,rsa4096 fit
+
+binman will extract FIT container, sign and replace it immediately.
+
+If you want to sign and replace FIT container in place::
+
+    $ binman sign -i image.bin -k privatekey -a sha256,rsa4096 -f fit.fit fit
+
+which will sign FIT container with private key and replace it immediately
+inside your image.
+
+
 Logging
 -------
 
-- 
2.39.1