arm64: dts: mediatek: mt6795: Add MMSYS node for multimedia clocks

Add the MultiMedia System node, providing clocks for the multimedia
hardware blocks and their IOMMU/SMIs.
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20230412112739.160376-18-angelogioacchino.delregno@collabora.comSigned-off-by: Matthias Brugger <matthias.bgg@gmail.com>

arch/arm64/boot/dts/mediatek/mt6795.dtsi

@@ -654,6 +654,19 @@ mmc3: mmc@11260000 {
 			status = "disabled";
 		};
 
+		mmsys: syscon@14000000 {
+			compatible = "mediatek,mt6795-mmsys", "syscon";
+			reg = <0 0x14000000 0 0x1000>;
+			power-domains = <&spm MT6795_POWER_DOMAIN_MM>;
+			assigned-clocks = <&topckgen CLK_TOP_MM_SEL>;
+			assigned-clock-rates = <400000000>;
+			#clock-cells = <1>;
+			#reset-cells = <1>;
+			mboxes = <&gce 0 CMDQ_THR_PRIO_HIGHEST>,
+				 <&gce 1 CMDQ_THR_PRIO_HIGHEST>;
+			mediatek,gce-client-reg = <&gce SUBSYS_1400XXXX 0 0x1000>;
+		};
+
 		vdecsys: clock-controller@16000000 {
 			compatible = "mediatek,mt6795-vdecsys";
 			reg = <0 0x16000000 0 0x1000>;