dt-bindings: timer: Add andestech atcpit100 timer binding doc

Andestech ATCPIT100 timer

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ATCPIT100 is a generic IP block from Andes Technology, embedded in

Andestech AE3XX platforms and other designs.

This timer is a set of compact multi-function timers, which can be

used as pulse width modulators (PWM) as well as simple timers.

It supports up to 4 PIT channels. Each PIT channel is a

multi-function timer and provide the following usage scenarios:

One 32-bit timer

Two 16-bit timers

Four 8-bit timers

One 16-bit PWM

One 16-bit timer and one 8-bit PWM

Two 8-bit timer and one 8-bit PWM

Required properties:

- compatible	: Should be "andestech,atcpit100"

- reg		: Address and length of the register set

- interrupts	: Reference to the timer interrupt

- clocks 	: a clock to provide the tick rate for "andestech,atcpit100"

- clock-names 	: should be "PCLK" for the peripheral clock source.

Examples:

timer0: timer@f0400000 {

	compatible = "andestech,atcpit100";

	reg = <0xf0400000 0x1000>;

	interrupts = <2>;

	clocks = <&apb>;

	clock-names = "PCLK";

};