The SoC specific strings supported including:
"hisilicon,hi3516cv300-pwm"
"hisilicon,hi3519v100-pwm"
+ "hisilicon,hi3559v100-shub-pwm"
+ "hisilicon,hi3559v100-pwm
- reg: physical base address and length of the controller's registers.
- clocks: phandle and clock specifier of the PWM reference clock.
- resets: phandle and reset specifier for the PWM controller reset.