dt-bindings: Move altr,msi-controller to interrupt-controller directory

While altr,msi-controller is used with PCI, it is not a PCI host bridge
and is just an MSI provider. Move it with other MSI providers in the
'interrupt-controller' directory.

Acked-by: Matthew Gerlach <matthew.gerlach@linux.intel.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20250507154253.1593870-1-robh@kernel.org
Signed-off-by: Rob Herring (Arm) <robh@kernel.org>

Documentation/devicetree/bindings/interrupt-controller/altr,msi-controller.yaml

@@ -0,0 +1,65 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+# Copyright (C) 2015, 2024, Intel Corporation
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/interrupt-controller/altr,msi-controller.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Altera PCIe MSI controller
+
+maintainers:
+  - Matthew Gerlach <matthew.gerlach@linux.intel.com>
+
+properties:
+  compatible:
+    enum:
+      - altr,msi-1.0
+
+  reg:
+    items:
+      - description: CSR registers
+      - description: Vectors slave port region
+
+  reg-names:
+    items:
+      - const: csr
+      - const: vector_slave
+
+  interrupts:
+    maxItems: 1
+
+  msi-controller: true
+
+  num-vectors:
+    description: number of vectors
+    $ref: /schemas/types.yaml#/definitions/uint32
+    minimum: 1
+    maximum: 32
+
+required:
+  - compatible
+  - reg
+  - reg-names
+  - interrupts
+  - msi-controller
+  - num-vectors
+
+allOf:
+  - $ref: /schemas/interrupt-controller/msi-controller.yaml#
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/arm-gic.h>
+    #include <dt-bindings/interrupt-controller/irq.h>
+    msi@ff200000 {
+        compatible = "altr,msi-1.0";
+        reg = <0xff200000 0x00000010>,
+              <0xff200010 0x00000080>;
+        reg-names = "csr", "vector_slave";
+        interrupt-parent = <&hps_0_arm_gic_0>;
+        interrupts = <GIC_SPI 42 IRQ_TYPE_LEVEL_HIGH>;
+        msi-controller;
+        num-vectors = <32>;
+    };