dt-bindings: PCI: Add bindings for brcmstb's PCIe device

The DT bindings description of the brcmstb PCIe device is described.
This node can only be used for now on the Raspberry Pi 4.
Signed-off-by: Jim Quinlan <james.quinlan@broadcom.com>
Co-developed-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Andrew Murray <andrew.murray@arm.com>

Documentation/devicetree/bindings/pci/brcm,stb-pcie.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/pci/brcm,stb-pcie.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Brcmstb PCIe Host Controller Device Tree Bindings
+
+maintainers:
+  - Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
+
+allOf:
+  - $ref: /schemas/pci/pci-bus.yaml#
+
+properties:
+  compatible:
+    const: brcm,bcm2711-pcie # The Raspberry Pi 4
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    minItems: 1
+    maxItems: 2
+    items:
+      - description: PCIe host controller
+      - description: builtin MSI controller
+
+  interrupt-names:
+    minItems: 1
+    maxItems: 2
+    items:
+      - const: pcie
+      - const: msi
+
+  ranges:
+    maxItems: 1
+
+  dma-ranges:
+    maxItems: 1
+
+  clocks:
+    maxItems: 1
+
+  clock-names:
+    items:
+      - const: sw_pcie
+
+  msi-controller:
+    description: Identifies the node as an MSI controller.
+
+  msi-parent:
+    description: MSI controller the device is capable of using.
+
+  brcm,enable-ssc:
+    description: Indicates usage of spread-spectrum clocking.
+    type: boolean
+
+required:
+  - reg
+  - dma-ranges
+  - "#interrupt-cells"
+  - interrupts
+  - interrupt-names
+  - interrupt-map-mask
+  - interrupt-map
+  - msi-controller
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/irq.h>
+    #include <dt-bindings/interrupt-controller/arm-gic.h>
+
+    scb {
+            #address-cells = <2>;
+            #size-cells = <1>;
+            pcie0: pcie@7d500000 {
+                    compatible = "brcm,bcm2711-pcie";
+                    reg = <0x0 0x7d500000 0x9310>;
+                    device_type = "pci";
+                    #address-cells = <3>;
+                    #size-cells = <2>;
+                    #interrupt-cells = <1>;
+                    interrupts = <GIC_SPI 148 IRQ_TYPE_LEVEL_HIGH>,
+                                 <GIC_SPI 148 IRQ_TYPE_LEVEL_HIGH>;
+                    interrupt-names = "pcie", "msi";
+                    interrupt-map-mask = <0x0 0x0 0x0 0x7>;
+                    interrupt-map = <0 0 0 1 &gicv2 GIC_SPI 143 IRQ_TYPE_LEVEL_HIGH>;
+                    msi-parent = <&pcie0>;
+                    msi-controller;
+                    ranges = <0x02000000 0x0 0xf8000000 0x6 0x00000000 0x0 0x04000000>;
+                    dma-ranges = <0x02000000 0x0 0x00000000 0x0 0x00000000 0x0 0x80000000>;
+                    brcm,enable-ssc;
+            };
+    };