[media] media: et8ek8: add device tree binding documentation

Add device tree binding documentation for toshiba et8ek8 sensor.
Signed-off-by: Ivaylo Dimitrov <ivo.g.dimitrov.75@gmail.com>
Signed-off-by: Pavel Machek <pavel@ucw.cz>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

Documentation/devicetree/bindings/media/i2c/toshiba,et8ek8.txt

+Toshiba et8ek8 5MP sensor
+
+Toshiba et8ek8 5MP sensor is an image sensor found in Nokia N900 device
+
+More detailed documentation can be found in
+Documentation/devicetree/bindings/media/video-interfaces.txt .
+
+
+Mandatory properties
+--------------------
+
+- compatible: "toshiba,et8ek8"
+- reg: I2C address (0x3e, or an alternative address)
+- vana-supply: Analogue voltage supply (VANA), 2.8 volts
+- clocks: External clock to the sensor
+- clock-frequency: Frequency of the external clock to the sensor. Camera
+  driver will set this frequency on the external clock. The clock frequency is
+  a pre-determined frequency known to be suitable to the board.
+- reset-gpios: XSHUTDOWN GPIO. The XSHUTDOWN signal is active low. The sensor
+  is in hardware standby mode when the signal is in the low state.
+
+
+Endpoint node mandatory properties
+----------------------------------
+
+- remote-endpoint: A phandle to the bus receiver's endpoint node.
+
+
+Example
+-------
+
+&i2c3 {
+	clock-frequency = <400000>;
+
+	cam1: camera@3e {
+		compatible = "toshiba,et8ek8";
+		reg = <0x3e>;
+		vana-supply = <&vaux4>;
+		clocks = <&isp 0>;
+		clock-frequency = <9600000>;
+		reset-gpio = <&gpio4 6 GPIO_ACTIVE_HIGH>; /* 102 */
+		port {
+			csi_cam1: endpoint {
+				remote-endpoint = <&csi_out1>;
+			};
+		};
+	};
+};