dt-bindings: memory-controllers: Add Exynos5422 DMC device description

Add device tree bindings for a new Exynos5422 Dynamic Memory Controller
device.
Signed-off-by: Lukasz Luba <l.luba@partner.samsung.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>

Documentation/devicetree/bindings/memory-controllers/exynos5422-dmc.txt

+* Exynos5422 frequency and voltage scaling for Dynamic Memory Controller device
+
+The Samsung Exynos5422 SoC has DMC (Dynamic Memory Controller) to which the DRAM
+memory chips are connected. The driver is to monitor the controller in runtime
+and switch frequency and voltage. To monitor the usage of the controller in
+runtime, the driver uses the PPMU (Platform Performance Monitoring Unit), which
+is able to measure the current load of the memory.
+When 'userspace' governor is used for the driver, an application is able to
+switch the DMC and memory frequency.
+
+Required properties for DMC device for Exynos5422:
+- compatible: Should be "samsung,exynos5422-dmc".
+- clocks : list of clock specifiers, must contain an entry for each
+  required entry in clock-names for CLK_FOUT_SPLL, CLK_MOUT_SCLK_SPLL,
+  CLK_FF_DOUT_SPLL2, CLK_FOUT_BPLL, CLK_MOUT_BPLL, CLK_SCLK_BPLL,
+  CLK_MOUT_MX_MSPLL_CCORE, CLK_MOUT_MX_MSPLL_CCORE_PHY, CLK_MOUT_MCLK_CDREX,
+- clock-names : should include "fout_spll", "mout_sclk_spll", "ff_dout_spll2",
+  "fout_bpll", "mout_bpll", "sclk_bpll", "mout_mx_mspll_ccore",
+  "mout_mclk_cdrex"  entries
+- devfreq-events : phandles for PPMU devices connected to this DMC.
+- vdd-supply : phandle for voltage regulator which is connected.
+- reg : registers of two CDREX controllers.
+- operating-points-v2 : phandle for OPPs described in v2 definition.
+- device-handle : phandle of the connected DRAM memory device. For more
+	information please refer to documentation file:
+	Documentation/devicetree/bindings/ddr/lpddr3.txt
+- devfreq-events : phandles of the PPMU events used by the controller.
+- samsung,syscon-clk : phandle of the clock register set used by the controller,
+	these registers are used for enabling a 'pause' feature and are not
+	exposed by clock framework but they must be used in a safe way.
+	The register offsets are in the driver code and specyfic for this SoC
+	type.
+
+Example:
+
+	ppmu_dmc0_0: ppmu@10d00000 {
+		compatible = "samsung,exynos-ppmu";
+		reg = <0x10d00000 0x2000>;
+		clocks = <&clock CLK_PCLK_PPMU_DREX0_0>;
+		clock-names = "ppmu";
+		events {
+			ppmu_event_dmc0_0: ppmu-event3-dmc0_0 {
+				event-name = "ppmu-event3-dmc0_0";
+			};
+		};
+	};
+
+	dmc: memory-controller@10c20000 {
+		compatible = "samsung,exynos5422-dmc";
+		reg = <0x10c20000 0x100>, <0x10c30000 0x100>,
+		clocks = <&clock CLK_FOUT_SPLL>,
+			 <&clock CLK_MOUT_SCLK_SPLL>,
+			 <&clock CLK_FF_DOUT_SPLL2>,
+			 <&clock CLK_FOUT_BPLL>,
+			 <&clock CLK_MOUT_BPLL>,
+			 <&clock CLK_SCLK_BPLL>,
+			 <&clock CLK_MOUT_MX_MSPLL_CCORE>,
+			 <&clock CLK_MOUT_MCLK_CDREX>,
+		clock-names = "fout_spll",
+			      "mout_sclk_spll",
+			      "ff_dout_spll2",
+			      "fout_bpll",
+			      "mout_bpll",
+			      "sclk_bpll",
+			      "mout_mx_mspll_ccore",
+			      "mout_mclk_cdrex",
+		operating-points-v2 = <&dmc_opp_table>;
+		devfreq-events = <&ppmu_event3_dmc0_0>,	<&ppmu_event3_dmc0_1>,
+				<&ppmu_event3_dmc1_0>, <&ppmu_event3_dmc1_1>;
+		device-handle = <&samsung_K3QF2F20DB>;
+		vdd-supply = <&buck1_reg>;
+		samsung,syscon-clk = <&clock>;
+	};