dt-bindings: i2c: Add binding for Actions Semiconductor Owl I2C controller

Add devicetree binding for Actions Semiconductor Owl I2C controller
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

Documentation/devicetree/bindings/i2c/i2c-owl.txt

+Actions Semiconductor Owl I2C controller
+
+Required properties:
+
+- compatible        : Should be "actions,s900-i2c".
+- reg               : Offset and length of the register set for the device.
+- #address-cells    : Should be 1.
+- #size-cells       : Should be 0.
+- interrupts        : A single interrupt specifier.
+- clocks            : Phandle of the clock feeding the I2C controller.
+
+Optional properties:
+
+- clock-frequency   : Desired I2C bus clock frequency in Hz. As only Normal and
+                      Fast modes are supported, possible values are 100000 and
+                      400000.
+Examples:
+
+        i2c0: i2c@e0170000 {
+                compatible = "actions,s900-i2c";
+                reg = <0 0xe0170000 0 0x1000>;
+                #address-cells = <1>;
+                #size-cells = <0>;
+                interrupts = <GIC_SPI 25 IRQ_TYPE_LEVEL_HIGH>;
+                clocks = <&clock CLK_I2C0>;
+                clock-frequency = <100000>;
+        };