[PATCH V4 1/3] dt-bindings: Add optional gpio property to uartps node to support rs485

[Manikanta Guntupalli <manikanta.guntupalli@amd.com>]

Add optional gpio property to uartps node and reference to rs485.yaml

On Xilinx/AMD Kria SOM KD240 board rs485 connects via TI ISOW1432
Transceiver device, where one GPIO is used for driving DE/RE signals.
With rs485 half duplex configuration, DE and RE are shorted to each other,
and at a time, any node acts as either a driver or a receiver.

Here,
DE - Driver enable. If pin is floating, driver is disabled.
RE - Receiver enable. If pin is floating, receiver buffer is disabled.

For more deatils, please find below link which contains Transceiver
device(ISOW1432) datasheet
https://www.ti.com/lit/ds/symlink/isow1432.pdf?ts=1682607122706&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FISOW1432%252Fpart-details%252FISOW1432DFMR%253FkeyMatch%253DISOW1432DFMR%2526tisearch%253Dsearch-everything%2526usecase%253DOPN

rts-gpios is optional property, because it is not required
for uart console node.

Signed-off-by: Manikanta Guntupalli <manikanta.guntupalli@amd.com>
---
Changes for V2:
Modify optional gpio name to xlnx,phy-ctrl-gpios.
Update commit description.

Changes for V3:
Modify optional gpio name to rts-gpios.
Update commit description.

Changes for V4:
Update rts-gpios description.
---
 Documentation/devicetree/bindings/serial/cdns,uart.yaml | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/Documentation/devicetree/bindings/serial/cdns,uart.yaml b/Documentation/devicetree/bindings/serial/cdns,uart.yaml
index e35ad1109efc..d5dd4e92d1fb 100644
--- a/Documentation/devicetree/bindings/serial/cdns,uart.yaml
+++ b/Documentation/devicetree/bindings/serial/cdns,uart.yaml
@@ -46,6 +46,10 @@ properties:
   power-domains:
     maxItems: 1
 
+  rts-gpios:
+    description: Optional GPIO to control transmit/receive.
+    maxItems: 1
+
 required:
   - compatible
   - reg
@@ -55,6 +59,7 @@ required:
 
 allOf:
   - $ref: serial.yaml#
+  - $ref: rs485.yaml#
   - if:
       properties:
         compatible:
-- 
2.25.1