dt-bindings: PCI: ti,j721e: Add binding to represent refclk to the connector

Add binding to represent refclk to the PCIe connector.

Link: https://lore.kernel.org/r/20210308063550.6227-2-kishon@ti.comSigned-off-by: NKishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: NLorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: NRob Herring <robh@kernel.org>

Documentation/devicetree/bindings/pci/ti,j721e-pci-host.yaml

@@ -46,12 +46,17 @@ properties:
     maxItems: 1
 
   clocks:
-    maxItems: 1
-    description: clock-specifier to represent input to the PCIe
+    minItems: 1
+    maxItems: 2
+    description: |+
+      clock-specifier to represent input to the PCIe for 1 item.
+      2nd item if present represents reference clock to the connector.
 
   clock-names:
+    minItems: 1
     items:
       - const: fck
+      - const: pcie_refclk
 
   vendor-id:
     const: 0x104c