media: dt-bindings: media: rcar-vin: Describe optional ep properties

Describe the optional endpoint properties for endpoint nodes of the R-Car
VIN interface device tree bindings documentation.
Signed-off-by: NJacopo Mondi <jacopo+renesas@jmondi.org>
Acked-by: NNiklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Reviewed-by: NRob Herring <robh@kernel.org>
Signed-off-by: NSakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab+samsung@kernel.org>

Documentation/devicetree/bindings/media/rcar_vin.txt

@@ -45,6 +45,17 @@ The per-board settings Gen2 platforms:
   Only the first one will be considered as each vin interface has one
   input port.
 
+  - Optional properties for endpoint nodes:
+    - hsync-active: see [1] for description. Default is active high.
+    - vsync-active: see [1] for description. Default is active high.
+      If both HSYNC and VSYNC polarities are not specified, embedded
+      synchronization is selected.
+    - field-active-even: see [1] for description. Default is active high.
+    - bus-width: see [1] for description. The selected bus width depends on
+      the SoC type and selected input image format.
+      Valid values are: 8, 10, 12, 16, 24 and 32.
+    - data-shift: see [1] for description. Valid values are 0 and 8.
+
 The per-board settings Gen3 platforms:
 
 Gen3 platforms can support both a single connected parallel input source
@@ -57,6 +68,10 @@ from local SoC CSI-2 receivers (port@1) depending on SoC.
       from external SoC pins as described in video-interfaces.txt[1].
       Describing more than one endpoint in port@0 is invalid. Only VIN
       instances that are connected to external pins should have port@0.
+
+      Endpoint nodes of port@0 support the optional properties listed in
+      the Gen2 per-board settings description.
+
     - port@1 - sub-nodes describing one or more endpoints connected to
       the VIN from local SoC CSI-2 receivers. The endpoint numbers must
       use the following schema.
@@ -66,6 +81,8 @@ from local SoC CSI-2 receivers (port@1) depending on SoC.
         - endpoint@2 - sub-node describing the endpoint connected to CSI40
         - endpoint@3 - sub-node describing the endpoint connected to CSI41
 
+      Endpoint nodes of port@1 do not support any optional endpoint property.
+
 Device node example for Gen2 platforms
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