dt-bindings: PCI: altera: Add binding for Agilex

Add the compatible bindings for the three variants of the Agilex
PCIe Hard IP.

Signed-off-by: Matthew Gerlach <matthew.gerlach@linux.intel.com>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Acked-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Link: https://lore.kernel.org/r/20250221170452.875419-2-matthew.gerlach@linux.intel.com
[kwilczynski: update description within devicetree bindings]
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>

Author: matthew-gerlach

Documentation/devicetree/bindings/pci/altr,pcie-root-port.yaml

@@ -12,9 +12,19 @@ maintainers:
 
 properties:
   compatible:
+    description: Each family of socfpga has its own implementation of the
+      PCI controller. The altr,pcie-root-port-1.0 is used for the Cyclone5
+      family of chips. The Stratix10 family of chips is supported by the
+      altr,pcie-root-port-2.0. The Agilex family of chips has three,
+      non-register compatible, variants of PCIe Hard IP referred to as the
+      F-Tile, P-Tile, and R-Tile, depending on the specific chip instance.
+
     enum:
       - altr,pcie-root-port-1.0
       - altr,pcie-root-port-2.0
+      - altr,pcie-root-port-3.0-f-tile
+      - altr,pcie-root-port-3.0-p-tile
+      - altr,pcie-root-port-3.0-r-tile
 
   reg:
     items: