dt-bindings: net: Introduce the ethernet-connector description

The ability to describe the physical ports of Ethernet devices is useful
to describe multi-port devices, as well as to remove any ambiguity with
regard to the nature of the port.

Moreover, describing ports allows for a better description of features
that are tied to connectors, such as PoE through the PSE-PD devices.

Introduce a binding to allow describing the ports, for now with 2
attributes :

- The number of pairs, which is a quite generic property that allows
differentating between multiple similar technologies such as BaseT1
and "regular" BaseT (which usually means BaseT4).

- The media that can be used on that port, such as BaseT for Twisted
Copper, BaseC for coax copper, BaseS/L for Fiber, BaseK for backplane
ethernet, etc. This allows defining the nature of the port, and
therefore avoids the need for vendor-specific properties such as
"micrel,fiber-mode" or "ti,fiber-mode".

The port description lives in its own file, as it is intended in the
future to allow describing the ports for phy-less devices.

Signed-off-by: Maxime Chevallier <[e-mail]>
Reviewed-by: Rob Herring (Arm) <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

Documentation/devicetree/bindings/net/ethernet-connector.yaml

···
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/net/ethernet-connector.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Generic Ethernet Connector
+
+maintainers:
+  - Maxime Chevallier <[e-mail]>
+
+description:
+  An Ethernet Connector represents the output of a network component such as
+  a PHY, an Ethernet controller with no PHY, or an SFP module.
+
+properties:
+
+  pairs:
+    description:
+      Defines the number of BaseT pairs that are used on the connector.
+    $ref: /schemas/types.yaml#/definitions/uint32
+    enum: [1, 2, 4]
+
+  media:
+    description:
+      The mediums, as defined in 802.3, that can be used on the port.
+    enum:
+      - BaseT
+      - BaseK
+      - BaseS
+      - BaseC
+      - BaseL
+      - BaseD
+      - BaseE
+      - BaseF
+      - BaseV
+      - BaseMLD
+
+required:
+  - media
+
+allOf:
+  - if:
+      properties:
+        media:
+          const: BaseT
+    then:
+      required:
+        - pairs
+    else:
+      properties:
+        pairs: false
+
+additionalProperties: true
+
+...

Documentation/devicetree/bindings/net/ethernet-phy.yaml

···
 
     additionalProperties: false
 
+  mdi:
+    type: object
+
+    patternProperties:
+      '^connector-[0-9]+$':
+        $ref: /schemas/net/ethernet-connector.yaml#
+
+        unevaluatedProperties: false
+
+    additionalProperties: false
+
 required:
   - reg
 
···
                     color = <LED_COLOR_ID_WHITE>;
                     function = LED_FUNCTION_LAN;
                     default-state = "keep";
+                };
+            };
+            /* Fast Ethernet port, with only 2 pairs wired */
+            mdi {
+                connector-0 {
+                    pairs = <2>;
+                    media = "BaseT";
                 };
             };
         };

MAINTAINERS

···
 L:	[e-mail]
 S:	Maintained
 F:	Documentation/ABI/testing/sysfs-class-net-phydev
+F:	Documentation/devicetree/bindings/net/ethernet-connector.yaml
 F:	Documentation/devicetree/bindings/net/ethernet-phy.yaml
 F:	Documentation/devicetree/bindings/net/mdio*
 F:	Documentation/devicetree/bindings/net/qca,ar803x.yaml