VIA/Wondermedia VT8500/WM8xxx series SoC PWM controller

Required properties:
- compatible: should be "via,vt8500-pwm"
- reg: physical base address and length of the controller's registers
- #pwm-cells: should be 3. See pwm.yaml in this directory for a description of
  the cells format. The only third cell flag supported by this binding is
  PWM_POLARITY_INVERTED.
- clocks: phandle to the PWM source clock

Example:

pwm1: pwm@d8220000 {
	#pwm-cells = <3>;
	compatible = "via,vt8500-pwm";
	reg = <0xd8220000 0x1000>;
	clocks = <&clkpwm>;
};
