dt-bindings: gpio: max3191x: Document new driver

Add device tree bindings for Maxim MAX3191x industrial serializer.

Cc: Mathias Duckeck <m.duckeck@kunbus.de>
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

diff --git a/Documentation/devicetree/bindings/gpio/gpio-max3191x.txt b/Documentation/devicetree/bindings/gpio/gpio-max3191x.txt
new file mode 100644 (file)
index 0000000..b3a6444
--- /dev/null
+++ b/Documentation/devicetree/bindings/gpio/gpio-max3191x.txt
@@ -0,0 +1,59 @@
+GPIO driver for Maxim MAX3191x industrial serializer
+
+Required properties:
+ - compatible:         Must be one of:
+                       "maxim,max31910"
+                       "maxim,max31911"
+                       "maxim,max31912"
+                       "maxim,max31913"
+                       "maxim,max31953"
+                       "maxim,max31963"
+ - reg:                Chip select number.
+ - gpio-controller:    Marks the device node as a GPIO controller.
+ - #gpio-cells:        Should be two. For consumer use see gpio.txt.
+
+Optional properties:
+ - #daisy-chained-devices:
+                       Number of chips in the daisy-chain (default is 1).
+ - maxim,modesel-gpios: GPIO pins to configure modesel of each chip.
+                       The number of GPIOs must equal "#daisy-chained-devices"
+                       (if each chip is driven by a separate pin) or 1
+                       (if all chips are wired to the same pin).
+ - maxim,fault-gpios:  GPIO pins to read fault of each chip.
+                       The number of GPIOs must equal "#daisy-chained-devices"
+                       or 1.
+ - maxim,db0-gpios:    GPIO pins to configure debounce of each chip.
+                       The number of GPIOs must equal "#daisy-chained-devices"
+                       or 1.
+ - maxim,db1-gpios:    GPIO pins to configure debounce of each chip.
+                       The number of GPIOs must equal "maxim,db0-gpios".
+ - maxim,modesel-8bit: Boolean whether the modesel pin of the chips is
+                       pulled high (8-bit mode).  Use this if the modesel pin
+                       is hardwired and consequently "maxim,modesel-gpios"
+                       cannot be specified.  By default if neither this nor
+                       "maxim,modesel-gpios" is given, the driver assumes
+                       that modesel is pulled low (16-bit mode).
+ - maxim,ignore-undervoltage:
+                       Boolean whether to ignore undervoltage alarms signaled
+                       by the "maxim,fault-gpios" or by the status byte
+                       (in 16-bit mode).  Use this if the chips are powered
+                       through 5VOUT instead of VCC24V, in which case they
+                       will constantly signal undervoltage.
+
+For other required and optional properties of SPI slave nodes please refer to
+../spi/spi-bus.txt.
+
+Example:
+       gpio@0 {
+               compatible = "maxim,max31913";
+               reg = <0>;
+               gpio-controller;
+               #gpio-cells = <2>;
+
+               maxim,modesel-gpios = <&gpio2 23>;
+               maxim,fault-gpios   = <&gpio2 24 GPIO_ACTIVE_LOW>;
+               maxim,db0-gpios     = <&gpio2 25>;
+               maxim,db1-gpios     = <&gpio2 26>;
+
+               spi-max-frequency = <25000000>;
+       };