Doc/DT: ti,omap4-dss: hdmi lanes

Add documentation for defining HDMI lane functions and polarities.
Signed-off-by: NTomi Valkeinen <tomi.valkeinen@ti.com>
Cc: devicetree@vger.kernel.org

Documentation/devicetree/bindings/video/ti,omap4-dss.txt

@@ -109,3 +109,7 @@ Required properties:
 
 Optional nodes:
 - Video port for HDMI output
+
+HDMI Endpoint optional properties:
+- lanes: list of 8 pin numbers for the HDMI lanes: CLK+, CLK-, D0+, D0-,
+  D1+, D1-, D2+, D2-. (default: 0,1,2,3,4,5,6,7)