linux/Documentation/devicetree/bindings/pps/pps-gpio.txt
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   1Device-Tree Bindings for a PPS Signal on GPIO
   2
   3These properties describe a PPS (pulse-per-second) signal connected to
   4a GPIO pin.
   5
   6Required properties:
   7- compatible: should be "pps-gpio"
   8- gpios: one PPS GPIO in the format described by ../gpio/gpio.txt
   9
  10Optional properties:
  11- assert-falling-edge: when present, assert is indicated by a falling edge
  12                       (instead of by a rising edge)
  13
  14Example:
  15        pps {
  16                compatible = "pps-gpio";
  17                gpios = <&gpio2 6 0>;
  18
  19                assert-falling-edge;
  20        };
  21