Understanding DMA and DT bindings
DT binding for the DMA channel depends on the DMA controller node, which is SoC-dependent, and some parameters (such as DMA cells) may vary from one SoC to another. This example only focuses on the i.MX SDMA controller, which can be found in the kernel source, at Documentation/devicetree/bindings/dma/fsl-imx-sdma.txt.
Consumer binding
According to the SDMA event-mapping table, the following code shows the DMA request signals for peripherals in i.MX 6Dual/6Quad:
uart1: serial@02020000 {
compatible = "fsl,imx6sx-uart", "fsl,imx21-uart";
reg = <0x02020000 0x4000>;
interrupts = <GIC_SPI 26 IRQ_TYPE_LEVEL_HIGH>;
clocks = <&clks IMX6SX_CLK_UART_IPG>,
<&clks IMX6SX_CLK_UART_SERIAL>;
...