media: dt: bindings: Add a binding for flash LED devices associated to a sensor

Camera flash drivers (and LEDs) are separate from the sensor devices in
DT. In order to make an association between the two, provide the
association information to the software.
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Cc: devicetree@vger.kernel.org
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Pavel Machek <pavel@ucw.cz>
Acked-by: Rob Herring <robh@kernel.org>
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

Documentation/devicetree/bindings/media/video-interfaces.txt

@@ -76,6 +76,14 @@ are required in a relevant parent node:
 		    identifier, should be 1.
  - #size-cells    : should be zero.
 
+
+Optional properties
+-------------------
+
+- flash-leds: An array of phandles, each referring to a flash LED, a sub-node
+  of the LED driver device node.
+
+
 Optional endpoint properties
 ----------------------------