ARM: STi: STiH415: Add reset controller support.

This patch adds a reset controller node to the SOC device tree and also
adds new header files with reset lines required for other device tree
nodes.
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@st.com>

Documentation/devicetree/bindings/reset/st,sti-powerdown.txt

+STMicroelectronics STi family Sysconfig Peripheral Powerdown Reset Controller
+=============================================================================
+
+This binding describes a reset controller device that is used to enable and
+disable on-chip peripheral controllers such as USB and SATA, using
+"powerdown" control bits found in the STi family SoC system configuration
+registers. These have been grouped together into a single reset controller
+device for convenience.
+
+The actual action taken when powerdown is asserted is hardware dependent.
+However, when asserted it may not be possible to access the hardware's
+registers and after an assert/deassert sequence the hardware's previous state
+may no longer be valid.
+
+Please refer to reset.txt in this directory for common reset
+controller binding usage.
+
+Required properties:
+- compatible: Should be "st,<chip>-powerdown"
+	ex: "st,stih415-powerdown", "st,stih416-powerdown"
+- #reset-cells: 1, see below
+
+example:
+
+	powerdown: powerdown-controller {
+		#reset-cells = <1>;
+		compatible = "st,stih415-powerdown";
+	};
+
+
+Specifying powerdown control of devices
+=======================================
+
+Device nodes should specify the reset channel required in their "resets"
+property, containing a phandle to the powerdown device node and an
+index specifying which channel to use, as described in reset.txt
+
+example:
+
+	usb1: usb@fe200000 {
+		resets	= <&powerdown STIH41X_USB1_POWERDOWN>;
+	};
+
+Macro definitions for the supported reset channels can be found in:
+
+include/dt-bindings/reset-controller/stih415-resets.h
+include/dt-bindings/reset-controller/stih416-resets.h

arch/arm/boot/dts/stih415.dtsi

@@ -10,6 +10,7 @@
 #include "stih415-clock.dtsi"
 #include "stih415-pinctrl.dtsi"
 #include <dt-bindings/interrupt-controller/arm-gic.h>
+#include <dt-bindings/reset-controller/stih415-resets.h>
 / {
 
 	L2: cache-controller {
@@ -28,6 +29,11 @@ soc {
 		ranges;
 		compatible	= "simple-bus";
 
+		powerdown: powerdown-controller {
+			#reset-cells = <1>;
+			compatible = "st,stih415-powerdown";
+		};
+
 		syscfg_sbc: sbc-syscfg@fe600000{
 			compatible      = "st,stih415-sbc-syscfg", "syscon";
 			reg		= <0xfe600000 0xb4>;

include/dt-bindings/reset-controller/stih415-resets.h

+/*
+ * This header provides constants for the reset controller
+ * based peripheral powerdown requests on the STMicroelectronics
+ * STiH415 SoC.
+ */
+#ifndef _DT_BINDINGS_RESET_CONTROLLER_STIH415
+#define _DT_BINDINGS_RESET_CONTROLLER_STIH415
+
+#define STIH415_EMISS_POWERDOWN		0
+#define STIH415_NAND_POWERDOWN		1
+#define STIH415_KEYSCAN_POWERDOWN	2
+#define STIH415_USB0_POWERDOWN		3
+#define STIH415_USB1_POWERDOWN		4
+#define STIH415_USB2_POWERDOWN		5
+#define STIH415_SATA0_POWERDOWN		6
+#define STIH415_SATA1_POWERDOWN		7
+#define STIH415_PCIE_POWERDOWN		8
+
+#endif /* _DT_BINDINGS_RESET_CONTROLLER_STIH415 */