media: dt-bindings: Add OF properties to ov7670

Describe newly introduced OF properties for ov7670 image sensor.
The driver supports two standard properties to configure synchronism
signals polarities and one custom property already supported as
platform data options to suppress pixel clock during horizontal
blankings.

Re-phrase child nodes description while at there.

Signed-off-by: Jacopo Mondi <[e-mail]>
Reviewed-by: Rob Herring <[e-mail]>
Signed-off-by: Sakari Ailus <[e-mail]>
Signed-off-by: Mauro Carvalho Chehab <[e-mail]>

Documentation/devicetree/bindings/media/i2c/ov7670.txt

···
 - clocks: reference to the xclk input clock.
 - clock-names: should be "xclk".
 
+Required Endpoint Properties:
+- hsync-active: active state of the HSYNC signal, 0/1 for LOW/HIGH respectively.
+- vsync-active: active state of the VSYNC signal, 0/1 for LOW/HIGH respectively.
+
 Optional Properties:
 - reset-gpios: reference to the GPIO connected to the resetb pin, if any.
   Active is low.
 - powerdown-gpios: reference to the GPIO connected to the pwdn pin, if any.
   Active is high.
+- ov7670,pclk-hb-disable: a boolean property to suppress pixel clock output
+  signal during horizontal blankings.
 
-The device node must contain one 'port' child node for its digital output
-video port, in accordance with the video interface bindings defined in
+The device node must contain one 'port' child node with one 'endpoint' child
+sub-node for its digital output video port, in accordance with the video
+interface bindings defined in:
 Documentation/devicetree/bindings/media/video-interfaces.txt.
 
 Example:
···
 			assigned-clocks = <&pck0>;
 			assigned-clock-rates = <25000000>;
 
+			ov7670,pclk-hb-disable;
+
 			port {
 				ov7670_0: endpoint {
+					hsync-active = <0>;
+					vsync-active = <0>;
+
 					remote-endpoint = <&isi_0>;
 				};
 			};