linux/Documentation/devicetree/bindings/spi/spi-gpio.txt
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   1SPI-GPIO devicetree bindings
   2
   3Required properties:
   4
   5 - compatible: should be set to "spi-gpio"
   6 - #address-cells: should be set to <0x1>
   7 - ranges
   8 - gpio-sck: GPIO spec for the SCK line to use
   9 - gpio-miso: GPIO spec for the MISO line to use
  10 - gpio-mosi: GPIO spec for the MOSI line to use
  11 - cs-gpios: GPIOs to use for chipselect lines
  12 - num-chipselects: number of chipselect lines
  13
  14Example:
  15
  16        spi {
  17                compatible = "spi-gpio";
  18                #address-cells = <0x1>;
  19                ranges;
  20
  21                gpio-sck = <&gpio 95 0>;
  22                gpio-miso = <&gpio 98 0>;
  23                gpio-mosi = <&gpio 97 0>;
  24                cs-gpios = <&gpio 125 0>;
  25                num-chipselects = <1>;
  26
  27                /* clients */
  28        };
  29
  30