clk: add clock driver for MediaTek MT7620 SoC

This patch adds a clock driver for MediaTek MT7620 SoC.
This driver provides clock gate control as well as getting clock frequency
for CPU/SYS/XTAL and some peripherals.

Reviewed-by: Stefan Roese <sr@denx.de>
Signed-off-by: Weijie Gao <weijie.gao@mediatek.com>

include/dt-bindings/clock/mt7620-clk.h

@@ -0,0 +1,40 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2020 MediaTek Inc.
+ *
+ * Author:  Weijie Gao <weijie.gao@mediatek.com>
+ */
+
+#ifndef _DT_BINDINGS_MT7620_CLK_H_
+#define _DT_BINDINGS_MT7620_CLK_H_
+
+/* Base clocks */
+#define CLK_SYS				34
+#define CLK_CPU				33
+#define CLK_XTAL			32
+
+/* Peripheral clocks */
+#define CLK_SDHC			30
+#define CLK_MIPS_CNT			28
+#define CLK_PCIE			26
+#define CLK_UPHY_12M			25
+#define CLK_EPHY			24
+#define CLK_ESW				23
+#define CLK_UPHY_48M			22
+#define CLK_FE				21
+#define CLK_UARTL			19
+#define CLK_SPI				18
+#define CLK_I2S				17
+#define CLK_I2C				16
+#define CLK_NAND			15
+#define CLK_GDMA			14
+#define CLK_PIO				13
+#define CLK_UARTF			12
+#define CLK_PCM				11
+#define CLK_MC				10
+#define CLK_INTC			9
+#define CLK_TIMER			8
+#define CLK_GE2				7
+#define CLK_GE1				6
+
+#endif /* _DT_BINDINGS_MT7620_CLK_H_ */