dt-bindings: pci: amlogic, meson-pcie: Add G12A bindings

Add PCIE bindings for the Amlogic G12A SoC, the support is the same
but the PHY is shared with USB3 to control the differential lines.

Thus this adds a phy phandle to control the PHY, and only requires the
MIPI clock for the Amlogic AXG SoC Family.
Signed-off-by: NNeil Armstrong <narmstrong@baylibre.com>
Signed-off-by: NLorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: NRob Herring <robh@kernel.org>
Reviewed-by: NAndrew Murray <andrew.murray@arm.com>

Documentation/devicetree/bindings/pci/amlogic,meson-pcie.txt

@@ -9,13 +9,16 @@ Additional properties are described here:
 
 Required properties:
 - compatible:
-	should contain "amlogic,axg-pcie" to identify the core.
+	should contain :
+	- "amlogic,axg-pcie" for AXG SoC Family
+	- "amlogic,g12a-pcie" for G12A SoC Family
+	to identify the core.
 - reg:
 	should contain the configuration address space.
 - reg-names: Must be
 	- "elbi"	External local bus interface registers
 	- "cfg"		Meson specific registers
-	- "phy"		Meson PCIE PHY registers
+	- "phy"		Meson PCIE PHY registers for AXG SoC Family
 	- "config"	PCIe configuration space
 - reset-gpios: The GPIO to generate PCIe PERST# assert and deassert signal.
 - clocks: Must contain an entry for each entry in clock-names.
@@ -23,12 +26,13 @@ Required properties:
 	- "pclk"       PCIe GEN 100M PLL clock
 	- "port"       PCIe_x(A or B) RC clock gate
 	- "general"    PCIe Phy clock
-	- "mipi"       PCIe_x(A or B) 100M ref clock gate
+	- "mipi"       PCIe_x(A or B) 100M ref clock gate for AXG SoC Family
 - resets: phandle to the reset lines.
 - reset-names: must contain "phy" "port" and "apb"
-       - "phy"         Share PHY reset
+       - "phy"         Share PHY reset for AXG SoC Family
        - "port"        Port A or B reset
        - "apb"         Share APB reset
+- phys: should contain a phandle to the shared phy for G12A SoC Family
 - device_type:
 	should be "pci". As specified in designware-pcie.txt