iio: distance: add dt binding for devantech-srf04

This patch adds dt binding for devantech ultrasonic ranger srf04.

The vendor "devantech" was already added to the vendor list with
        "[PATCH v4 1/3] iio: distance: srf08: add trivial DT binding"

Signed-off-by: Andreas Klinger <ak@it-klinger.de>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

diff --git a/Documentation/devicetree/bindings/iio/proximity/devantech-srf04.txt b/Documentation/devicetree/bindings/iio/proximity/devantech-srf04.txt
new file mode 100644 (file)
index 0000000..d4dc7a2
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/proximity/devantech-srf04.txt
@@ -0,0 +1,28 @@
+* Devantech SRF04 ultrasonic range finder
+  Bit-banging driver using two GPIOs
+
+Required properties:
+ - compatible: Should be "devantech,srf04"
+
+ - trig-gpios: Definition of the GPIO for the triggering (output)
+               This GPIO is set for about 10 us by the driver to tell the
+               device it should initiate the measurement cycle.
+
+ - echo-gpios: Definition of the GPIO for the echo (input)
+               This GPIO is set by the device as soon as an ultrasonic
+               burst is sent out and reset when the first echo is
+               received.
+               Thus this GPIO is set while the ultrasonic waves are doing
+               one round trip.
+               It needs to be an GPIO which is able to deliver an
+               interrupt because the time between two interrupts is
+               measured in the driver.
+               See Documentation/devicetree/bindings/gpio/gpio.txt for
+               information on how to specify a consumer gpio.
+
+Example:
+srf04@0 {
+       compatible = "devantech,srf04";
+       trig-gpios = <&gpio1 15 GPIO_ACTIVE_HIGH>;
+       echo-gpios = <&gpio2  6 GPIO_ACTIVE_HIGH>;
+};