dt-bindings: add binding for the Allwinner DE2 CCU

Allwinner "Display Engine 2.0" contains some clock controls in it.

In order to add them as clock drivers, we need a device tree binding.
Add the binding here.

Also add the device tree binding headers.

Signed-off-by: Icenowy Zheng <[e-mail]>
Acked-by: Rob Herring <[e-mail]>
Signed-off-by: Maxime Ripard <[e-mail]>

Documentation/devicetree/bindings/clock/sun8i-de2.txt

···
+Allwinner Display Engine 2.0 Clock Control Binding
+--------------------------------------------------
+
+Required properties :
+- compatible: must contain one of the following compatibles:
+		- "allwinner,sun8i-a83t-de2-clk"
+		- "allwinner,sun8i-v3s-de2-clk"
+		- "allwinner,sun50i-h5-de2-clk"
+
+- reg: Must contain the registers base address and length
+- clocks: phandle to the clocks feeding the display engine subsystem.
+	  Three are needed:
+  - "mod": the display engine module clock
+  - "bus": the bus clock for the whole display engine subsystem
+- clock-names: Must contain the clock names described just above
+- resets: phandle to the reset control for the display engine subsystem.
+- #clock-cells : must contain 1
+- #reset-cells : must contain 1
+
+Example:
+de2_clocks: clock@1000000 {
+	compatible = "allwinner,sun8i-a83t-de2-clk";
+	reg = <0x01000000 0x100000>;
+	clocks = <&ccu CLK_BUS_DE>,
+		 <&ccu CLK_DE>;
+	clock-names = "bus",
+		      "mod";
+	resets = <&ccu RST_BUS_DE>;
+	#clock-cells = <1>;
+	#reset-cells = <1>;
+};

include/dt-bindings/clock/sun8i-de2.h

···
+/*
+ * Copyright (C) 2016 Icenowy Zheng <[e-mail]>
+ *
+ * SPDX-License-Identifier: (GPL-2.0+ OR MIT)
+ */
+
+#ifndef _DT_BINDINGS_CLOCK_SUN8I_DE2_H_
+#define _DT_BINDINGS_CLOCK_SUN8I_DE2_H_
+
+#define CLK_BUS_MIXER0		0
+#define CLK_BUS_MIXER1		1
+#define CLK_BUS_WB		2
+
+#define CLK_MIXER0		6
+#define CLK_MIXER1		7
+#define CLK_WB			8
+
+#endif /* _DT_BINDINGS_CLOCK_SUN8I_DE2_H_ */

include/dt-bindings/reset/sun8i-de2.h

···
+/*
+ * Copyright (C) 2016 Icenowy Zheng <[e-mail]>
+ *
+ * SPDX-License-Identifier: (GPL-2.0+ OR MIT)
+ */
+
+#ifndef _DT_BINDINGS_RESET_SUN8I_DE2_H_
+#define _DT_BINDINGS_RESET_SUN8I_DE2_H_
+
+#define RST_MIXER0	0
+#define RST_MIXER1	1
+#define RST_WB		2
+
+#endif /* _DT_BINDINGS_RESET_SUN8I_DE2_H_ */