linux/Documentation/devicetree/bindings/rtc/rtc-cmos.txt
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   1 Motorola mc146818 compatible RTC
   2~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   3
   4Required properties:
   5  - compatible : "motorola,mc146818"
   6  - reg : should contain registers location and length.
   7
   8Optional properties:
   9  - interrupts : should contain interrupt.
  10  - interrupt-parent : interrupt source phandle.
  11  - ctrl-reg : Contains the initial value of the control register also
  12    called "Register B".
  13  - freq-reg : Contains the initial value of the frequency register also
  14    called "Regsiter A".
  15
  16"Register A" and "B" are usually initialized by the firmware (BIOS for
  17instance). If this is not done, it can be performed by the driver.
  18
  19ISA Example:
  20
  21        rtc@70 {
  22                 compatible = "motorola,mc146818";
  23                 interrupts = <8 3>;
  24                 interrupt-parent = <&ioapic1>;
  25                 ctrl-reg = <2>;
  26                 freq-reg = <0x26>;
  27                 reg = <1 0x70 2>;
  28         };
  29