dt-bindings: misc: Describe TI FPC202 dual port controller

The FPC202 dual port controller serves as a low speed signal aggregator for
common port types, notably SFP. It provides access to I2C and low-speed
GPIO signals of a downstream device through a single upstream control
interface.

Up to two logical I2C addresses can be accessed on each of the FPC202's
ports. The port controller acts as an I2C translator (ATR). It converts
addresses of incoming and outgoing I2C transactions. One use case of this
is accessing two SFP modules at logical address 0x50 from the same upstream
I2C controller, using two different client aliases.

Reviewed-by: Conor Dooley <[e-mail]>
Tested-by: Tomi Valkeinen <[e-mail]>
Signed-off-by: Romain Gantois <[e-mail]>
Acked-by: Andi Shyti <[e-mail]>
Signed-off-by: Wolfram Sang <[e-mail]>

Documentation/devicetree/bindings/misc/ti,fpc202.yaml

···
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/misc/ti,fpc202.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: TI FPC202 dual port controller with expanded IOs
+
+maintainers:
+  - Romain Gantois <[e-mail]>
+
+allOf:
+  - $ref: /schemas/i2c/i2c-atr.yaml#
+
+properties:
+  compatible:
+    const: ti,fpc202
+
+  reg:
+    maxItems: 1
+
+  gpio-controller: true
+
+  "#gpio-cells":
+    const: 2
+
+  enable-gpios:
+    description:
+      Specifier for the GPIO connected to the EN pin.
+    maxItems: 1
+
+  '#address-cells':
+    const: 1
+
+  '#size-cells':
+    const: 0
+
+patternProperties:
+  "^i2c@[0-1]$":
+    $ref: /schemas/i2c/i2c-controller.yaml#
+    description: Downstream device ports 0 and 1
+
+    properties:
+      reg:
+        maxItems: 1
+        description:
+          Downstream port ID
+
+    required:
+      - "#address-cells"
+      - "#size-cells"
+      - reg
+
+    unevaluatedProperties: false
+
+required:
+  - compatible
+  - reg
+  - gpio-controller
+  - "#gpio-cells"
+  - "#address-cells"
+  - "#size-cells"
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        i2c-atr@f {
+            compatible = "ti,fpc202";
+            reg = <0xf>;
+            #address-cells = <1>;
+            #size-cells = <0>;
+
+            gpio-controller;
+            #gpio-cells = <2>;
+
+            i2c@0 {
+                #address-cells = <1>;
+                #size-cells = <0>;
+                reg = <0>;
+            };
+
+            i2c@1 {
+                #address-cells = <1>;
+                #size-cells = <0>;
+                reg = <1>;
+            };
+        };
+    };
+...

MAINTAINERS

···
 F:	drivers/mmc/host/tifm_sd.c
 F:	include/linux/tifm.h
 
+TI FPC202 DUAL PORT CONTROLLER
+M:	Romain Gantois <[e-mail]>
+L:	[e-mail]
+S:	Maintained
+F:	Documentation/devicetree/bindings/misc/ti,fpc202.yaml
+
 TI FPD-LINK DRIVERS
 M:	Tomi Valkeinen <[e-mail]>
 L:	[e-mail]