devicetree: Add new SKY81452 mfd binding

Signed-off-by: NGyungoh Yoo <jack.yoo@skyworksinc.com>
Signed-off-by: NLee Jones <lee.jones@linaro.org>

Documentation/devicetree/bindings/mfd/sky81452.txt

+SKY81452 bindings
+
+Required properties:
+- compatible	: Must be "skyworks,sky81452"
+- reg		: I2C slave address
+
+Required child nodes:
+- backlight	: container node for backlight following the binding
+		in video/backlight/sky81452-backlight.txt
+- regulator	: container node for regulators following the binding
+		in regulator/sky81452-regulator.txt
+
+Example:
+
+	sky81452@2c {
+		compatible = "skyworks,sky81452";
+		reg = <0x2c>;
+
+		backlight {
+			compatible = "skyworks,sky81452-backlight";
+			name = "pwm-backlight";
+			led-sources = <0 1 2 3 6>;
+			skyworks,ignore-pwm;
+			skyworks,phase-shift;
+			skyworks,current-limit = <2300>;
+		};
+
+		regulator {
+			lout {
+				regulator-name = "sky81452-lout";
+				regulator-min-microvolt = <4500000>;
+				regulator-max-microvolt = <8000000>;
+			};
+		};
+	};