* sun6i Real Time Clock

RTC controller for the Allwinner A31

Required properties:
- compatible	: Should be one of the following combinations:
		    - "allwinner,sun6i-a31-rtc"
		    - "allwinner,sun8i-a23-rtc"
		    - "allwinner,sun8i-h3-rtc"
		    - "allwinner,sun8i-r40-rtc", "allwinner,sun8i-h3-rtc"
		    - "allwinner,sun8i-v3-rtc"
		    - "allwinner,sun50i-a64-rtc", "allwinner,sun8i-h3-rtc"
		    - "allwinner,sun50i-h5-rtc"

		  Where there are two or more compatible strings, this
		  denotes the hardware covered by the most specific one
		  is backward-compatible with the latter ones, and the
		  implementation for the latter ones can be used, albeit
		  with reduced functionality.

- reg		: physical base address of the controller and length of
		  memory mapped region.
- interrupts	: IRQ lines for the RTC alarm 0 and alarm 1, in that order.

Required properties for new device trees
- clocks	: phandle to the 32kHz external oscillator
- clock-output-names : names of up to three clock outputs. See below.
- #clock-cells  : must be equal to 1.

The RTC provides the following clocks at the given indices:
- 0: LOSC
- 1: LOSC external output, known as X32KFOUT in the datasheet.
     This clock is not available on the A31 and is deprecated for old
     device trees still using the "allwinner,sun6i-a31-rtc" compatible.
- 2: InternalOSC, or internal RC oscillator (A64/H3/H5 only)

Example:

rtc: rtc@1f00000 {
	compatible = "allwinner,sun6i-a31-rtc";
	reg = <0x01f00000 0x400>;
	interrupts = <0 40 4>, <0 41 4>;
	clock-output-names = "osc32k";
	clocks = <&ext_osc32k>;
	#clock-cells = <1>;
};