dt-bindings: dma: uart: rename binding

The filename matches mtk-uart-apdma.c.
So using "mtk-uart-apdma.txt" should be better.
And add some property.

Signed-off-by: Long Cheng <long.cheng@mediatek.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Vinod Koul <vkoul@kernel.org>

Documentation/devicetree/bindings/dma/mtk-uart-apdma.txt

@@ -0,0 +1,54 @@
+* Mediatek UART APDMA Controller
+
+Required properties:
+- compatible should contain:
+  * "mediatek,mt2712-uart-dma" for MT2712 compatible APDMA
+  * "mediatek,mt6577-uart-dma" for MT6577 and all of the above
+
+- reg: The base address of the APDMA register bank.
+
+- interrupts: A single interrupt specifier.
+ One interrupt per dma-requests, or 8 if no dma-requests property is present
+
+- dma-requests: The number of DMA channels
+
+- clocks : Must contain an entry for each entry in clock-names.
+  See ../clocks/clock-bindings.txt for details.
+- clock-names: The APDMA clock for register accesses
+
+- mediatek,dma-33bits: Present if the DMA requires support
+
+Examples:
+
+	apdma: dma-controller@11000400 {
+		compatible = "mediatek,mt2712-uart-dma";
+		reg = <0 0x11000400 0 0x80>,
+		      <0 0x11000480 0 0x80>,
+		      <0 0x11000500 0 0x80>,
+		      <0 0x11000580 0 0x80>,
+		      <0 0x11000600 0 0x80>,
+		      <0 0x11000680 0 0x80>,
+		      <0 0x11000700 0 0x80>,
+		      <0 0x11000780 0 0x80>,
+		      <0 0x11000800 0 0x80>,
+		      <0 0x11000880 0 0x80>,
+		      <0 0x11000900 0 0x80>,
+		      <0 0x11000980 0 0x80>;
+		interrupts = <GIC_SPI 103 IRQ_TYPE_LEVEL_LOW>,
+			     <GIC_SPI 104 IRQ_TYPE_LEVEL_LOW>,
+			     <GIC_SPI 105 IRQ_TYPE_LEVEL_LOW>,
+			     <GIC_SPI 106 IRQ_TYPE_LEVEL_LOW>,
+			     <GIC_SPI 107 IRQ_TYPE_LEVEL_LOW>,
+			     <GIC_SPI 108 IRQ_TYPE_LEVEL_LOW>,
+			     <GIC_SPI 109 IRQ_TYPE_LEVEL_LOW>,
+			     <GIC_SPI 110 IRQ_TYPE_LEVEL_LOW>,
+			     <GIC_SPI 111 IRQ_TYPE_LEVEL_LOW>,
+			     <GIC_SPI 112 IRQ_TYPE_LEVEL_LOW>,
+			     <GIC_SPI 113 IRQ_TYPE_LEVEL_LOW>,
+			     <GIC_SPI 114 IRQ_TYPE_LEVEL_LOW>;
+		dma-requests = <12>;
+		clocks = <&pericfg CLK_PERI_AP_DMA>;
+		clock-names = "apdma";
+		mediatek,dma-33bits;
+		#dma-cells = <1>;
+	};