mfd: ac100: Add device tree bindings for X-Powers AC100 codec/RTC combo IC

X-Powers AC100 Codec/RTC IC Device Tree bindings

AC100 is a audio codec and RTC subsystem combo IC. The 2 parts are

separated, including power supplies and interrupt lines, but share

a common register address space and host interface.

Required properties:

- compatible: "x-powers,ac100"

- reg: The I2C slave address or RSB hardware address for the chip

- sub-nodes:

  - codec

    - compatible:		"x-powers,ac100-codec"

    - interrupt-parent:		The parent interrupt controller

    - interrupts:		SoC NMI / GPIO interrupt connected to the

    				IRQ_AUDIO pin

    - #clock-cells:		Shall be 0

    - clock-output-names:	"4M_adda"

    - see clock/clock-bindings.txt for common clock bindings

  - rtc

    - compatible:		"x-powers,ac100-rtc"

    - interrupt-parent:		The parent interrupt controller

    - interrupts:		SoC NMI / GPIO interrupt connected to the

    				IRQ_RTC pin

    - clocks:			A phandle to the codec's "4M_adda" clock

    - #clock-cells:		Shall be 1

    - clock-output-names:	"cko1_rtc", "cko2_rtc", "cko3_rtc"

    - see clock/clock-bindings.txt for common clock bindings

Example:

ac100: codec@e89 {

	compatible = "x-powers,ac100";

	reg = <0xe89>;

	ac100_codec: codec {

		compatible = "x-powers,ac100-codec";

		interrupt-parent = <&r_pio>;

		interrupts = <0 9 IRQ_TYPE_LEVEL_LOW>; /* PL9 */

		#clock-cells = <0>;

		clock-output-names = "4M_adda";

	};

	ac100_rtc: rtc {

		compatible = "x-powers,ac100-rtc";

		interrupt-parent = <&nmi_intc>;

		interrupts = <0 IRQ_TYPE_LEVEL_LOW>;

		clocks = <&ac100_codec>;

		#clock-cells = <1>;

		clock-output-names = "cko1_rtc", "cko2_rtc", "cko3_rtc";

	};

};