dt-bindings: document the STM32 RTC bindings

This patch adds documentation of device tree bindings for the STM32 RTC.

Signed-off-by: Amelie Delaunay <amelie.delaunay@st.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>

diff --git a/Documentation/devicetree/bindings/rtc/st,stm32-rtc.txt b/Documentation/devicetree/bindings/rtc/st,stm32-rtc.txt
new file mode 100644 (file)
index 0000000..e2837b9
--- /dev/null
+++ b/Documentation/devicetree/bindings/rtc/st,stm32-rtc.txt
@@ -0,0 +1,27 @@
+STM32 Real Time Clock
+
+Required properties:
+- compatible: "st,stm32-rtc".
+- reg: address range of rtc register set.
+- clocks: reference to the clock entry ck_rtc.
+- interrupt-parent: phandle for the interrupt controller.
+- interrupts: rtc alarm interrupt.
+- st,syscfg: phandle for pwrcfg, mandatory to disable/enable backup domain
+  (RTC registers) write protection.
+
+Optional properties (to override default ck_rtc parent clock):
+- assigned-clocks: reference to the ck_rtc clock entry.
+- assigned-clock-parents: phandle of the new parent clock of ck_rtc.
+
+Example:
+
+       rtc: rtc@40002800 {
+               compatible = "st,stm32-rtc";
+               reg = <0x40002800 0x400>;
+               clocks = <&rcc 1 CLK_RTC>;
+               assigned-clocks = <&rcc 1 CLK_RTC>;
+               assigned-clock-parents = <&rcc 1 CLK_LSE>;
+               interrupt-parent = <&exti>;
+               interrupts = <17 1>;
+               st,syscfg = <&pwrcfg>;
+       };