bus: ixp4xx: Add DT bindings for the IXP4xx expansion bus

This adds device tree bindings for the IXP4xx expansion bus controller.

Cc: Marc Zyngier <maz@kernel.org>
Cc: devicetree@vger.kernel.org
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

Documentation/devicetree/bindings/bus/intel,ixp4xx-expansion-bus-controller.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/bus/intel,ixp4xx-expansion-bus-controller.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Intel IXP4xx Expansion Bus Controller
+
+description: |
+  The IXP4xx expansion bus controller handles access to devices on the
+  memory-mapped expansion bus on the Intel IXP4xx family of system on chips,
+  including IXP42x, IXP43x, IXP45x and IXP46x.
+
+maintainers:
+  - Linus Walleij <linus.walleij@linaro.org>
+
+properties:
+  $nodename:
+    pattern: '^bus@[0-9a-f]+$'
+
+  compatible:
+    items:
+      - enum:
+          - intel,ixp42x-expansion-bus-controller
+          - intel,ixp43x-expansion-bus-controller
+          - intel,ixp45x-expansion-bus-controller
+          - intel,ixp46x-expansion-bus-controller
+      - const: syscon
+
+  reg:
+    description: Control registers for the expansion bus, these are not
+      inside the memory range handled by the expansion bus.
+    maxItems: 1
+
+  native-endian:
+    $ref: /schemas/types.yaml#/definitions/flag
+    description: The IXP4xx has a peculiar MMIO access scheme, as it changes
+      the access pattern for words (swizzling) on the bus depending on whether
+      the SoC is running in big-endian or little-endian mode. Thus the
+      registers must always be accessed using native endianness.
+
+  "#address-cells":
+    description: |
+      The first cell is the chip select number.
+      The second cell is the address offset within the bank.
+    const: 2
+
+  "#size-cells":
+    const: 1
+
+  ranges: true
+  dma-ranges: true
+
+patternProperties:
+  "^.*@[0-7],[0-9a-f]+$":
+    description: Devices attached to chip selects are represented as
+      subnodes.
+    type: object
+
+    properties:
+      intel,ixp4xx-eb-t1:
+        description: Address timing, extend address phase with n cycles.
+        $ref: /schemas/types.yaml#/definitions/uint32
+        maximum: 3
+
+      intel,ixp4xx-eb-t2:
+        description: Setup chip select timing, extend setup phase with n cycles.
+        $ref: /schemas/types.yaml#/definitions/uint32
+        maximum: 3
+
+      intel,ixp4xx-eb-t3:
+        description: Strobe timing, extend strobe phase with n cycles.
+        $ref: /schemas/types.yaml#/definitions/uint32
+        maximum: 15
+
+      intel,ixp4xx-eb-t4:
+        description: Hold timing, extend hold phase with n cycles.
+        $ref: /schemas/types.yaml#/definitions/uint32
+        maximum: 3
+
+      intel,ixp4xx-eb-t5:
+        description: Recovery timing, extend recovery phase with n cycles.
+        $ref: /schemas/types.yaml#/definitions/uint32
+        maximum: 15
+
+      intel,ixp4xx-eb-cycle-type:
+        description: The type of cycles to use on the expansion bus for this
+          chip select. 0 = Intel cycles, 1 = Motorola cycles, 2 = HPI cycles.
+        $ref: /schemas/types.yaml#/definitions/uint32
+        enum: [0, 1, 2]
+
+      intel,ixp4xx-eb-byte-access-on-halfword:
+        description: Allow byte read access on half word devices.
+        $ref: /schemas/types.yaml#/definitions/uint32
+        enum: [0, 1]
+
+      intel,ixp4xx-eb-hpi-hrdy-pol-high:
+        description: Set HPI HRDY polarity to active high when using HPI.
+        $ref: /schemas/types.yaml#/definitions/uint32
+        enum: [0, 1]
+
+      intel,ixp4xx-eb-mux-address-and-data:
+        description: Multiplex address and data on the data bus.
+        $ref: /schemas/types.yaml#/definitions/uint32
+        enum: [0, 1]
+
+      intel,ixp4xx-eb-ahb-split-transfers:
+        description: Enable AHB split transfers.
+        $ref: /schemas/types.yaml#/definitions/uint32
+        enum: [0, 1]
+
+      intel,ixp4xx-eb-write-enable:
+        description: Enable write cycles.
+        $ref: /schemas/types.yaml#/definitions/uint32
+        enum: [0, 1]
+
+      intel,ixp4xx-eb-byte-access:
+        description: Expansion bus uses only 8 bits. The default is to use
+          16 bits.
+        $ref: /schemas/types.yaml#/definitions/uint32
+        enum: [0, 1]
+
+required:
+  - compatible
+  - reg
+  - native-endian
+  - "#address-cells"
+  - "#size-cells"
+  - ranges
+  - dma-ranges
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/irq.h>
+    bus@50000000 {
+        compatible = "intel,ixp42x-expansion-bus-controller", "syscon";
+        reg = <0xc4000000 0x28>;
+        native-endian;
+        #address-cells = <2>;
+        #size-cells = <1>;
+        ranges = <0 0x0 0x50000000 0x01000000>,
+                 <1 0x0 0x51000000 0x01000000>;
+        dma-ranges = <0 0x0 0x50000000 0x01000000>,
+                     <1 0x0 0x51000000 0x01000000>;
+        flash@0,0 {
+            compatible = "intel,ixp4xx-flash", "cfi-flash";
+            bank-width = <2>;
+            reg = <0 0x00000000 0x1000000>;
+            intel,ixp4xx-eb-t3 = <3>;
+            intel,ixp4xx-eb-cycle-type = <0>;
+            intel,ixp4xx-eb-byte-access-on-halfword = <1>;
+            intel,ixp4xx-eb-write-enable = <1>;
+            intel,ixp4xx-eb-byte-access = <0>;
+        };
+        serial@1,0 {
+            compatible = "exar,xr16l2551", "ns8250";
+            reg = <1 0x00000000 0x10>;
+            interrupt-parent = <&gpio0>;
+            interrupts = <4 IRQ_TYPE_LEVEL_LOW>;
+            clock-frequency = <1843200>;
+            intel,ixp4xx-eb-t3 = <3>;
+            intel,ixp4xx-eb-cycle-type = <1>;
+            intel,ixp4xx-eb-write-enable = <1>;
+            intel,ixp4xx-eb-byte-access = <1>;
+        };
+    };