dt-bindings: phy: Add sparx5-serdes bindings

Document the Sparx5 ethernet serdes phy driver bindings.
Signed-off-by: Lars Povlsen <lars.povlsen@microchip.com>
Signed-off-by: Steen Hegelund <steen.hegelund@microchip.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20210218161451.3489955-2-steen.hegelund@microchip.comSigned-off-by: Vinod Koul <vkoul@kernel.org>

Documentation/devicetree/bindings/phy/microchip,sparx5-serdes.yaml

+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/phy/microchip,sparx5-serdes.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Microchip Sparx5 Serdes controller
+
+maintainers:
+  - Steen Hegelund <steen.hegelund@microchip.com>
+
+description: |
+  The Sparx5 SERDES interfaces share the same basic functionality, but
+  support different operating modes and line rates.
+
+  The following list lists the SERDES features:
+
+  * RX Adaptive Decision Feedback Equalizer (DFE)
+  * Programmable continuous time linear equalizer (CTLE)
+  * Rx variable gain control
+  * Rx built-in fault detector (loss-of-lock/loss-of-signal)
+  * Adjustable tx de-emphasis (FFE)
+  * Tx output amplitude control
+  * Supports rx eye monitor
+  * Multiple loopback modes
+  * Prbs generator and checker
+  * Polarity inversion control
+
+  SERDES6G:
+
+  The SERDES6G is a high-speed SERDES interface, which can operate at
+  the following data rates:
+
+  * 100 Mbps (100BASE-FX)
+  * 1.25 Gbps (SGMII/1000BASE-X/1000BASE-KX)
+  * 3.125 Gbps (2.5GBASE-X/2.5GBASE-KX)
+  * 5.15625 Gbps (5GBASE-KR/5G-USXGMII)
+
+  SERDES10G
+
+  The SERDES10G is a high-speed SERDES interface, which can operate at
+  the following data rates:
+
+  * 100 Mbps (100BASE-FX)
+  * 1.25 Gbps (SGMII/1000BASE-X/1000BASE-KX)
+  * 3.125 Gbps (2.5GBASE-X/2.5GBASE-KX)
+  * 5 Gbps (QSGMII/USGMII)
+  * 5.15625 Gbps (5GBASE-KR/5G-USXGMII)
+  * 10 Gbps (10G-USGMII)
+  * 10.3125 Gbps (10GBASE-R/10GBASE-KR/USXGMII)
+
+  SERDES25G
+
+  The SERDES25G is a high-speed SERDES interface, which can operate at
+  the following data rates:
+
+  * 1.25 Gbps (SGMII/1000BASE-X/1000BASE-KX)
+  * 3.125 Gbps (2.5GBASE-X/2.5GBASE-KX)
+  * 5 Gbps (QSGMII/USGMII)
+  * 5.15625 Gbps (5GBASE-KR/5G-USXGMII)
+  * 10 Gbps (10G-USGMII)
+  * 10.3125 Gbps (10GBASE-R/10GBASE-KR/USXGMII)
+  * 25.78125 Gbps (25GBASE-KR/25GBASE-CR/25GBASE-SR/25GBASE-LR/25GBASE-ER)
+
+properties:
+  $nodename:
+    pattern: "^serdes@[0-9a-f]+$"
+
+  compatible:
+    const: microchip,sparx5-serdes
+
+  reg:
+    minItems: 1
+
+  '#phy-cells':
+    const: 1
+    description: |
+      - The main serdes input port
+
+  clocks:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+  - '#phy-cells'
+  - clocks
+
+additionalProperties: false
+
+examples:
+  - |
+    serdes: serdes@10808000 {
+      compatible = "microchip,sparx5-serdes";
+      #phy-cells = <1>;
+      clocks = <&sys_clk>;
+      reg = <0x10808000 0x5d0000>;
+    };
+
+...