bindings: Add dt-bindings for arch_timer

Add snapshot of dt-bindings for arch_timer
This is a snapshot from msm-4.14 commit
("4da722ca19").

Change-Id: I065711e62ede9f46d81d46710c6ace3fd754a56c

bindings/arm/arch_timer.txt

@@ -0,0 +1,112 @@
+* ARM architected timer
+
+ARM cores may have a per-core architected timer, which provides per-cpu timers,
+or a memory mapped architected timer, which provides up to 8 frames with a
+physical and optional virtual timer per frame.
+
+The per-core architected timer is attached to a GIC to deliver its
+per-processor interrupts via PPIs. The memory mapped timer is attached to a GIC
+to deliver its interrupts via SPIs.
+
+** CP15 Timer node properties:
+
+- compatible : Should at least contain one of
+	"arm,armv7-timer"
+	"arm,armv8-timer"
+
+- interrupts : Interrupt list for secure, non-secure, virtual and
+  hypervisor timers, in that order.
+
+- clock-frequency : The frequency of the main counter, in Hz. Should be present
+  only where necessary to work around broken firmware which does not configure
+  CNTFRQ on all CPUs to a uniform correct value. Use of this property is
+  strongly discouraged; fix your firmware unless absolutely impossible.
+
+- always-on : a boolean property. If present, the timer is powered through an
+  always-on power domain, therefore it never loses context.
+
+- fsl,erratum-a008585 : A boolean property. Indicates the presence of
+  QorIQ erratum A-008585, which says that reading the counter is
+  unreliable unless the same value is returned by back-to-back reads.
+  This also affects writes to the tval register, due to the implicit
+  counter read.
+
+- hisilicon,erratum-161010101 : A boolean property. Indicates the
+  presence of Hisilicon erratum 161010101, which says that reading the
+  counters is unreliable in some cases, and reads may return a value 32
+  beyond the correct value. This also affects writes to the tval
+  registers, due to the implicit counter read.
+
+** Optional properties:
+
+- arm,cpu-registers-not-fw-configured : Firmware does not initialize
+  any of the generic timer CPU registers, which contain their
+  architecturally-defined reset values. Only supported for 32-bit
+  systems which follow the ARMv7 architected reset values.
+
+- arm,no-tick-in-suspend : The main counter does not tick when the system is in
+  low-power system suspend on some SoCs. This behavior does not match the
+  Architecture Reference Manual's specification that the system counter "must
+  be implemented in an always-on power domain."
+
+
+Example:
+
+	timer {
+		compatible = "arm,cortex-a15-timer",
+			     "arm,armv7-timer";
+		interrupts = <1 13 0xf08>,
+			     <1 14 0xf08>,
+			     <1 11 0xf08>,
+			     <1 10 0xf08>;
+		clock-frequency = <100000000>;
+	};
+
+** Memory mapped timer node properties:
+
+- compatible : Should at least contain "arm,armv7-timer-mem".
+
+- clock-frequency : The frequency of the main counter, in Hz. Should be present
+  only when firmware has not configured the MMIO CNTFRQ registers.
+
+- reg : The control frame base address.
+
+Note that #address-cells, #size-cells, and ranges shall be present to ensure
+the CPU can address a frame's registers.
+
+A timer node has up to 8 frame sub-nodes, each with the following properties:
+
+- frame-number: 0 to 7.
+
+- interrupts : Interrupt list for physical and virtual timers in that order.
+  The virtual timer interrupt is optional.
+
+- reg : The first and second view base addresses in that order. The second view
+  base address is optional.
+
+- status : "disabled" indicates the frame is not available for use. Optional.
+
+Example:
+
+	timer@f0000000 {
+		compatible = "arm,armv7-timer-mem";
+		#address-cells = <1>;
+		#size-cells = <1>;
+		ranges;
+		reg = <0xf0000000 0x1000>;
+		clock-frequency = <50000000>;
+
+		frame@f0001000 {
+			frame-number = <0>
+			interrupts = <0 13 0x8>,
+				     <0 14 0x8>;
+			reg = <0xf0001000 0x1000>,
+			      <0xf0002000 0x1000>;
+		};
+
+		frame@f0003000 {
+			frame-number = <1>
+			interrupts = <0 15 0x8>;
+			reg = <0xf0003000 0x1000>;
+		};
+	};