Add dma support for lpuart. This function depend on DMA driver.
You can turn on it by write both the dmas and dma-name properties in dts node.

Signed-off-by: Yuan Yao <redacted>
Acked-by: Arnd Bergmann <arnd@arndb.de>
---
 .../devicetree/bindings/serial/fsl-lpuart.txt      |  19 +-
 drivers/tty/serial/fsl_lpuart.c                    | 430 ++++++++++++++++++++-
 2 files changed, 433 insertions(+), 16 deletions(-)

diff --git a/Documentation/devicetree/bindings/serial/fsl-lpuart.txt b/Documentation/devicetree/bindings/serial/fsl-lpuart.txt
index 6fd1dd1..6e1cbbf 100644
--- a/Documentation/devicetree/bindings/serial/fsl-lpuart.txt
+++ b/Documentation/devicetree/bindings/serial/fsl-lpuart.txt

@@ -5,10 +5,19 @@ Reqiuired properties:
 - reg : Address and length of the register set for the device
 - interrupts : Should contain uart interrupt

+Optional properties:
+- dmas: A list of two dma specifiers, one for each entry in dma-names.
+- dma-names: should contain "tx" and "rx".
+
+Note: Optional properties for DMA support. Write them both or both not.
+
 Example:

 uart0: serial at 40027000 {
-              compatible = "fsl,vf610-lpuart";
-              reg = <0x40027000 0x1000>;
-              interrupts = <0 61 0x00>;
-       };
+               compatible = "fsl,vf610-lpuart";
+               reg = <0x40027000 0x1000>;
+               interrupts = <0 61 0x00>;
+               dmas = <&edma0 0 2>,
+                       <&edma0 0 3>;
+               dma-names = "rx","tx";
+       };