[PATCH] Documentation: usb: document bbu fastboot partition name

[Bastian Krause <bst@pengutronix.de>]

After looking this up the nth time in the code base, it's really time to
document this.

Signed-off-by: Bastian Krause <bst@pengutronix.de>
---
 Documentation/user/usb.rst | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/Documentation/user/usb.rst b/Documentation/user/usb.rst
index 95d6dd7e363..92fe1234645 100644
--- a/Documentation/user/usb.rst
+++ b/Documentation/user/usb.rst
@@ -168,7 +168,8 @@ The Fastboot gadget supports the following commands:
 ``fastboot flash`` additionally supports image types UBI and Barebox. For UBI
 Images and a MTD device as target, ubiformat is called. For a Barebox image
 with an available barebox update handler for the fastboot exported device, the
-barebox_update is called.
+barebox_update is called (exported as ``bbu-<update_handler_name>`` fastboot
+partition).
 
 The barebox Fastboot gadget supports the following non standard extensions:
 
-- 
2.39.2