dt-bindings: leds: Add DT bindings for max77650

Add the DT binding document for the LEDs module of max77650.
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

Documentation/devicetree/bindings/leds/leds-max77650.txt

+LED driver for MAX77650 PMIC from Maxim Integrated.
+
+This module is part of the MAX77650 MFD device. For more details
+see Documentation/devicetree/bindings/mfd/max77650.txt.
+
+The LED controller is represented as a sub-node of the PMIC node on
+the device tree.
+
+This device has three current sinks.
+
+Required properties:
+--------------------
+- compatible:		Must be "maxim,max77650-led"
+- #address-cells:	Must be <1>.
+- #size-cells:		Must be <0>.
+
+Each LED is represented as a sub-node of the LED-controller node. Up to
+three sub-nodes can be defined.
+
+Required properties of the sub-node:
+------------------------------------
+
+- reg:			Must be <0>, <1> or <2>.
+
+Optional properties of the sub-node:
+------------------------------------
+
+- label:		See Documentation/devicetree/bindings/leds/common.txt
+- linux,default-trigger: See Documentation/devicetree/bindings/leds/common.txt
+
+For more details, please refer to the generic GPIO DT binding document
+<devicetree/bindings/gpio/gpio.txt>.
+
+Example:
+--------
+
+	leds {
+		compatible = "maxim,max77650-led";
+		#address-cells = <1>;
+		#size-cells = <0>;
+
+		led@0 {
+			reg = <0>;
+			label = "blue:usr0";
+		};
+
+		led@1 {
+			reg = <1>;
+			label = "red:usr1";
+			linux,default-trigger = "heartbeat";
+		};
+
+		led@2 {
+			reg = <2>;
+			label = "green:usr2";
+		};
+	};