dt-bindings: display: bridge: thc63lvd1024: Document dual-output mode

The DT binding support both dual-input and dual-output mode, but only
dual-input is documented. Document dual-output mode.
Suggested-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Acked-by: Jacopo Mondi <jacopo@jmondi.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>

Documentation/devicetree/bindings/display/bridge/thine,thc63lvd1024.yaml

@@ -30,11 +30,17 @@ properties:
       This device has four video ports. Their connections are modeled using the
       OF graph bindings specified in Documentation/devicetree/bindings/graph.txt.
 
-      The device can operate in single-link mode or dual-link mode. In
-      single-link mode, all pixels are received on port@0, and port@1 shall not
-      contain any endpoint. In dual-link mode, even-numbered pixels are
-      received on port@0 and odd-numbered pixels on port@1, and both port@0 and
-      port@1 shall contain endpoints.
+      The device can operate in single or dual input and output modes.
+
+      When operating in single input mode, all pixels are received on port@0,
+      and port@1 shall not contain any endpoint. In dual input mode,
+      even-numbered pixels are received on port@0 and odd-numbered pixels on
+      port@1, and both port@0 and port@1 shall contain endpoints.
+
+      When operating in single output mode all pixels are output from the first
+      CMOS/TTL port and port@3 shall not contain any endpoint. In dual output
+      mode pixels are output from both CMOS/TTL ports and both port@2 and
+      port@3 shall contain endpoints.
 
     properties:
       '#address-cells':