dt-binding: phy: Add i.MX8MP PCIe PHY binding

Add i.MX8MP PCIe PHY binding.
On i.MX8MM, the initialized default value of PERST bit(BIT3) of
SRC_PCIEPHY_RCR is 1b'1.
But i.MX8MP has one inversed default value 1b'0 of PERST bit.

And the PERST bit should be kept 1b'1 after power and clocks are stable.
So add one more PERST explicitly for i.MX8MP PCIe PHY.

Signed-off-by: Richard Zhu <[e-mail]>
Tested-by: Marek Vasut <[e-mail]>
Tested-by: Richard Leitner <[e-mail]>
Tested-by: Alexander Stein <[e-mail]>
Reviewed-by: Lucas Stach <[e-mail]>
Reviewed-by: Rob Herring <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Vinod Koul <[e-mail]>

Documentation/devicetree/bindings/phy/fsl,imx8-pcie-phy.yaml

···
   compatible:
     enum:
       - fsl,imx8mm-pcie-phy
+      - fsl,imx8mp-pcie-phy
 
   reg:
     maxItems: 1
···
       - const: ref
 
   resets:
-    maxItems: 1
+    minItems: 1
+    maxItems: 2
 
   reset-names:
-    items:
-      - const: pciephy
+    oneOf:
+      - items:          # for iMX8MM
+          - const: pciephy
+      - items:          # for IMX8MP
+          - const: pciephy
+          - const: perst
 
   fsl,refclk-pad-mode:
     description: |
···
     type: boolean
     description: A boolean property indicating the CLKREQ# signal is
       not supported in the board design (optional)
+
+  power-domains:
+    description: PCIe PHY  power domain (optional).
+    maxItems: 1
 
 required:
   - "#phy-cells"