dt-bindings: clock: mediatek: document clk bindings vcodecsys for Mediatek MT6765 SoC

This patch adds the binding documentation for vcodecsys.
Signed-off-by: Mars Cheng <mars.cheng@mediatek.com>
Signed-off-by: Owen Chen <owen.chen@mediatek.com>
Signed-off-by: Macpaul Lin <macpaul.lin@mediatek.com>
Link: https://lore.kernel.org/r/1582278742-1626-4-git-send-email-macpaul.lin@mediatek.comSigned-off-by: Stephen Boyd <sboyd@kernel.org>

Documentation/devicetree/bindings/arm/mediatek/mediatek,vcodecsys.txt

+Mediatek vcodecsys controller
+============================
+
+The Mediatek vcodecsys controller provides various clocks to the system.
+
+Required Properties:
+
+- compatible: Should be one of:
+	- "mediatek,mt6765-vcodecsys", "syscon"
+- #clock-cells: Must be 1
+
+The vcodecsys controller uses the common clk binding from
+Documentation/devicetree/bindings/clock/clock-bindings.txt
+The available clocks are defined in dt-bindings/clock/mt*-clk.h.
+
+The vcodecsys controller also uses the common power domain from
+Documentation/devicetree/bindings/soc/mediatek/scpsys.txt
+The available power doamins are defined in dt-bindings/power/mt*-power.h.
+
+Example:
+
+venc_gcon: clock-controller@17000000 {
+	compatible = "mediatek,mt6765-vcodecsys", "syscon";
+	reg = <0 0x17000000 0 0x10000>;
+	power-domains = <&scpsys MT6765_POWER_DOMAIN_VCODEC>;
+	#clock-cells = <1>;
+};