LED connected to PWM

Required properties:
- compatible : should be "pwm-leds".

Each LED is represented as a sub-node of the pwm-leds device.  Each
node's name represents the name of the corresponding LED.

LED sub-node properties:
- pwms : PWM property to point to the PWM device (phandle)/port (id) and to
  specify the period time to be used: <&phandle id period_ns>;
- pwm-names : (optional) Name to be used by the PWM subsystem for the PWM device
  For the pwms and pwm-names property please refer to:
  Documentation/devicetree/bindings/pwm/pwm.txt
- max-brightness : Maximum brightness possible for the LED
- active-low : (optional) For PWMs where the LED is wired to supply
  rather than ground.
- label :  (optional)
  see Documentation/devicetree/bindings/leds/common.txt
- linux,default-trigger :  (optional)
  see Documentation/devicetree/bindings/leds/common.txt

Example:

twl_pwm: pwm {
	/* provides two PWMs (id 0, 1 for PWM1 and PWM2) */
	compatible = "ti,twl6030-pwm";
	#pwm-cells = <2>;
};

twl_pwmled: pwmled {
	/* provides one PWM (id 0 for Charing indicator LED) */
	compatible = "ti,twl6030-pwmled";
	#pwm-cells = <2>;
};

pwmleds {
	compatible = "pwm-leds";
	kpad {
		label = "omap4::keypad";
		pwms = <&twl_pwm 0 7812500>;
		max-brightness = <127>;
	};

	charging {
		label = "omap4:green:chrg";
		pwms = <&twl_pwmled 0 7812500>;
		max-brightness = <255>;
	};
};
