dt_bindings: rs485: Add receiver enable polarity

Add polarity property for receiver enable. Some UARTs have separate
enable pins for tx (RTS or DE) and rx (RE). As most RS485 transceivers
have !RE pin, the default is active low in contrast to
rs485-rts-active-low that defaults to active high.

Cc: devicetree@vger.kernel.org
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20220426122448.38997-4-ilpo.jarvinen@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/Documentation/devicetree/bindings/serial/rs485.yaml b/Documentation/devicetree/bindings/serial/rs485.yaml
index 0c9fa694f85c840610b01dcb66370f3ee420fad1..f2c9c9fe6aa7da4703cc397c02c6df46bbf3e3e6 100644 (file)
--- a/Documentation/devicetree/bindings/serial/rs485.yaml
+++ b/Documentation/devicetree/bindings/serial/rs485.yaml
@@ -33,6 +33,11 @@ properties:
     description: drive RTS low when sending (default is high).
     $ref: /schemas/types.yaml#/definitions/flag
 
+  rs485-rx-active-high:
+    description: Polarity of receiver enable signal (when separate from RTS).
+      True indicates active high (default is low).
+    $ref: /schemas/types.yaml#/definitions/flag
+
   linux,rs485-enabled-at-boot-time:
     description: enables the rs485 feature at boot time. It can be disabled
       later with proper ioctl.