media: dt: bindings: media: Document practices for DT bindings, ports, endpoints

Port and endpoint numbering has been omitted in DT binding documentation
for a large number of devices. Also common properties the device uses have
been missed in binding documentation. Make it explicit that these things
need to be documented.
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

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

@@ -55,6 +55,15 @@ divided into two separate ITU-R BT.656 8-bit busses.  In such case bus-width
 and data-shift properties can be used to assign physical data lines to each
 endpoint node (logical bus).
 
+Documenting bindings for devices
+--------------------------------
+
+All required and optional bindings the device supports shall be explicitly
+documented in device DT binding documentation. This also includes port and
+endpoint nodes for the device, including unit-addresses and reg properties where
+relevant.
+
+Please also see Documentation/devicetree/bindings/graph.txt .
 
 Required properties
 -------------------