dt-bindings: rtc: new binding for Raspberry Pi RTC driver

Add binding for the new RTC driver for Raspberry Pi.
This platform has an RTC managed by firmware, and this RTC
driver provides the simple mailbox interface to access it.

Signed-off-by: Dom Cobley <popcornmix@gmail.com>

diff --git a/Documentation/devicetree/bindings/rtc/rtc-rpi.txt b/Documentation/devicetree/bindings/rtc/rtc-rpi.txt
new file mode 100644 (file)
index 0000000..bbbc28b
--- /dev/null
+++ b/Documentation/devicetree/bindings/rtc/rtc-rpi.txt
@@ -0,0 +1,17 @@
+* Raspberry Pi RTC
+
+This is a Linux interface to an RTC managed by firmware, hence it's
+virtual from a Linux perspective.
+
+The interface uses the firmware mailbox api to access the RTC registers.
+
+Required properties:
+compatible: should be "raspberrypi,rpi-rtc"
+firmware:   Reference to the RPi firmware device node.
+
+Example:
+
+       rpi_rtc: rpi_rtc {
+               compatible = "raspberrypi,rpi-rtc";
+               firmware = <&firmware>;
+       };