Add the possibility to get the clock-frequency from a timer clock instead
of specifying it as dt property. Additionally also add the possibility
to also define a controlling periphal clock for the timer block.

The clock-frequency property is kept to act as fallback if no clocks
are specified.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
---
 Documentation/devicetree/bindings/rtc/dw-apb.txt |   19 ++++++++++++++++
 drivers/clocksource/dw_apb_timer_of.c            |   26 +++++++++++++++++++++-
 2 files changed, 44 insertions(+), 1 deletions(-)

diff --git a/Documentation/devicetree/bindings/rtc/dw-apb.txt b/Documentation/devicetree/bindings/rtc/dw-apb.txt
index 93e2b0f..80ab1c1 100644
--- a/Documentation/devicetree/bindings/rtc/dw-apb.txt
+++ b/Documentation/devicetree/bindings/rtc/dw-apb.txt

@@ -5,9 +5,20 @@ Required properties:
 - reg: physical base address of the controller and length of memory mapped
   region.
 - interrupts: IRQ line for the timer.
+- either clocks+clock-names or clock-frequency properties
+
+Optional properties:
+- clocks	: list of clock specifiers, corresponding to entries in
+		  the clock-names property;
+- clock-names	: should contain "timer and "pclk" entries, matching entries