linux/Documentation/devicetree/bindings/gpio/gpio-samsung.txt
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   1Samsung Exynos4 GPIO Controller
   2
   3Required properties:
   4- compatible: Compatible property value should be "samsung,exynos4-gpio>".
   5
   6- reg: Physical base address of the controller and length of memory mapped
   7  region.
   8
   9- #gpio-cells: Should be 4. The syntax of the gpio specifier used by client nodes
  10  should be the following with values derived from the SoC user manual.
  11     <[phandle of the gpio controller node]
  12      [pin number within the gpio controller]
  13      [mux function]
  14      [flags and pull up/down]
  15      [drive strength]>
  16
  17  Values for gpio specifier:
  18  - Pin number: is a value between 0 to 7.
  19  - Flags and Pull Up/Down: 0 - Pull Up/Down Disabled.
  20                            1 - Pull Down Enabled.
  21                            3 - Pull Up Enabled.
  22          Bit 16 (0x00010000) - Input is active low.
  23  - Drive Strength: 0 - 1x,
  24                    1 - 3x,
  25                    2 - 2x,
  26                    3 - 4x
  27
  28- gpio-controller: Specifies that the node is a gpio controller.
  29- #address-cells: should be 1.
  30- #size-cells: should be 1.
  31
  32Example:
  33
  34        gpa0: gpio-controller@11400000 {
  35                #address-cells = <1>;
  36                #size-cells = <1>;
  37                compatible = "samsung,exynos4-gpio";
  38                reg = <0x11400000 0x20>;
  39                #gpio-cells = <4>;
  40                gpio-controller;
  41        };
  42