[PATCH 2/5] dt-bindings: rtc: Add optional property "prescaler" in APM X-Gene RTC Document

[wefu@redhat.com]

From: Wei Fu <wefu@redhat.com>

Add optional property "prescaler" for APM X-Gene RTC.
The clock source on some platform to RTC is NOT 1HZ,
so we need to prescale the clock to make the input clock become 1HZ,
like (32K/prescaler) = 1HZ on the XuanTie TH1520 AP sub-system RTC.

Signed-off-by: Wei Fu <wefu@redhat.com>
---
 .../devicetree/bindings/rtc/xgene-rtc.txt        | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/Documentation/devicetree/bindings/rtc/xgene-rtc.txt b/Documentation/devicetree/bindings/rtc/xgene-rtc.txt
index fd195c358446..25ba8cf0cc31 100644
--- a/Documentation/devicetree/bindings/rtc/xgene-rtc.txt
+++ b/Documentation/devicetree/bindings/rtc/xgene-rtc.txt
@@ -10,6 +10,9 @@ Required properties:
 - #clock-cells: Should be 1.
 - clocks: Reference to the clock entry.
 
+Optional properties:
+- prescaler: Reference to the Value of Counter Prescaler.
+
 Example:
 
 rtcclk: rtcclk {
@@ -26,3 +29,16 @@ rtc: rtc@10510000 {
 	#clock-cells = <1>;
 	clocks = <&rtcclk 0>;
 };
+
+Example XuanTie TH1520 RTC node with Counter Prescaler(prescaler):
+
+rtc: rtc@fffff40000 {
+	compatible = "snps,dw-apb-rtc";
+	reg = <0xff 0xfff40000 0x0 0x1000>;
+	interrupts = <74 IRQ_TYPE_LEVEL_HIGH>;
+	clocks = <&osc_32k>;
+	clock-names = "osc_32k";
+	wakeup-source;
+	prescaler = <0x8000>;
+	status = "okay";
+};
-- 
2.44.0