NXP PCF85263 I2C Real Time Clock

Required properties:
- compatible: must be: "nxp,rtc-pcf85263"
- reg: must be the I2C address

Optional properties:
- interrupt-names: Which interrupt signal is used must be "INTA" or "INTB"
    Defaults to "INTA"

- quartz-load-capacitance: The internal capacitor to select for the quartz:
	PCF85263_QUARTZCAP_7pF		[0]
	PCF85263_QUARTZCAP_6pF		[1]
	PCF85263_QUARTZCAP_12p5pF	[2] DEFAULT

- quartz-drive-strength: Drive strength for the quartz:
	PCF85263_QUARTZDRIVE_NORMAL	[0] DEFAULT
	PCF85263_QUARTZDRIVE_LOW	[1]
	PCF85263_QUARTZDRIVE_HIGH	[2]

- quartz-low-jitter: Boolean property, if present enables low jitter mode
which
    reduces jitter at the cost of increased power consumption.

- wakeup-source: mark the chip as a wakeup source, independently of
    the availability of an IRQ line connected to the SoC.
    This is useful if the IRQ line is connected to a PMIC or other circuit
    that can power up the device rather than to a normal SOC interrupt.

Example:

rtc@51 {
	compatible = "nxp,pcf85263";
	reg = <0x51>;

	interrupt-parent = <&gpio4>;
	interrupts = <5 IRQ_TYPE_LEVEL_LOW>;
	interrupt-names = "INTB";

	quartz-load-capacitance = <PCF85263_QUARTZCAP_12p5pF>;
	quartz-drive-strength = <PCF85263_QUARTZDRIVE_LOW>;
};