linux/Documentation/devicetree/bindings/input/pwm-beeper.txt
<<
>>
Prefs
   1* PWM beeper device tree bindings
   2
   3Registers a PWM device as beeper.
   4
   5Required properties:
   6- compatible: should be "pwm-beeper"
   7- pwms: phandle to the physical PWM device
   8