[PATCH v2 3/3] dt-bindings: serial: Add label property in serial.yaml

[Zhen Lei <thunder.leizhen@xxxxxxxxxx>]

When there is more than one serial port present, the property 'label'
allows a custom name to be used for briefly describe the usage or position
of each serial port.

Without this "label" property, many dtbs_check warnings similar to the
following are reported:
arch/arm64/boot/dts/hisilicon/hi3660-hikey960.dt.yaml: \
serial@ffd74000: Additional properties are not allowed ('label' was unexpected)
        From schema: Documentation/devicetree/bindings/serial/pl011.yaml

Signed-off-by: Zhen Lei <thunder.leizhen@xxxxxxxxxx>
---
 Documentation/devicetree/bindings/serial/serial.yaml | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/Documentation/devicetree/bindings/serial/serial.yaml b/Documentation/devicetree/bindings/serial/serial.yaml
index 71aec7fda07d..04ec229cbb4f 100644
--- a/Documentation/devicetree/bindings/serial/serial.yaml
+++ b/Documentation/devicetree/bindings/serial/serial.yaml
@@ -23,6 +23,8 @@ properties:
   $nodename:
     pattern: "^serial(@[0-9a-f,]+)?$"
 
+  label: true
+
   cts-gpios:
     maxItems: 1
     description:
-- 
2.21.1