Binding for Qualcomm Light Pulse Generator

The Qualcomm Light Pulse Generator consists of three different hardware blocks;
a ramp generator with lookup table, the light pulse generator and a three
channel current sink. These blocks are found in a wide range of Qualcomm PMICs.

Required properties:
- compatible: one of:
	      "qcom,pm8916-pwm",
	      "qcom,pm8941-lpg",
	      "qcom,pm8994-lpg",
	      "qcom,pmi8994-lpg",
	      "qcom,pmi8998-lpg",

Optional properties:
- qcom,power-source: power-source used to drive the output, as defined in the
		     datasheet. Should be specified if the TRILED block is
		     present
- qcom,dtest: configures the output into an internal test line of the
	      pmic. Specified by a list of u32 pairs, one pair per channel,
	      where each pair denotes the test line to drive and the second
	      configures how the value should be outputed, as defined in the
	      datasheet
- #pwm-cells: should be 2, see ../pwm/pwm.txt

LED subnodes:
A set of subnodes can be used to specify LEDs connected to the LPG. Channels
not associated with a LED are available as pwm channels, see ../pwm/pwm.txt.

Required properties:
- led-sources: list of channels associated with this LED, starting at 1 for the
	       first LPG channel

Optional properties:
- label: see Documentation/devicetree/bindings/leds/common.txt
- default-state: see Documentation/devicetree/bindings/leds/common.txt
- linux,default-trigger: see Documentation/devicetree/bindings/leds/common.txt

Example:
The following example defines a RGB LED attached to the PM8941.

&spmi_bus {
	pm8941@1 {
		lpg {
			compatible = "qcom,pm8941-lpg";
			qcom,power-source = <1>;

			rgb {
				led-sources = <7 6 5>;
			};
		};
	};
};

The following example defines the single PWM channel of the PM8916, which can
be muxed by the MPP4 as a current sink.

&spmi_bus {
	pm8916@1 {
		pm8916_pwm: pwm {
			compatible = "qcom,pm8916-pwm";

			#pwm-cells = <2>;
		};
	};
};
