dt-bindings: PCI: dra7xx: Add DT bindings for PCI dra7xx EP mode

Add device tree binding documentation for PCI dra7xx EP mode.
Acked-by: NRob Herring <robh@kernel.org>
Signed-off-by: NKishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>

Documentation/devicetree/bindings/pci/ti-pci.txt

 TI PCI Controllers
 
 PCIe Designware Controller
- - compatible: Should be "ti,dra7-pcie""
- - reg : Two register ranges as listed in the reg-names property
- - reg-names : The first entry must be "ti-conf" for the TI specific registers
-	       The second entry must be "rc-dbics" for the designware pcie
-	       registers
-	       The third entry must be "config" for the PCIe configuration space
+ - compatible: Should be "ti,dra7-pcie" for RC
+	       Should be "ti,dra7-pcie-ep" for EP
  - phys : list of PHY specifiers (used by generic PHY framework)
  - phy-names : must be "pcie-phy0", "pcie-phy1", "pcie-phyN".. based on the
 	       number of PHYs as specified in *phys* property.
  - ti,hwmods : Name of the hwmod associated to the pcie, "pcie<X>",
 	       where <X> is the instance number of the pcie from the HW spec.
+ - num-lanes as specified in ../designware-pcie.txt
+
+HOST MODE
+=========
+ - reg : Two register ranges as listed in the reg-names property
+ - reg-names : The first entry must be "ti-conf" for the TI specific registers
+	       The second entry must be "rc-dbics" for the DesignWare PCIe
+	       registers
+	       The third entry must be "config" for the PCIe configuration space
  - interrupts : Two interrupt entries must be specified. The first one is for
 		main interrupt line and the second for MSI interrupt line.
  - #address-cells,
@@ -19,13 +24,31 @@ PCIe Designware Controller
    #interrupt-cells,
    device_type,
    ranges,
-   num-lanes,
    interrupt-map-mask,
    interrupt-map : as specified in ../designware-pcie.txt
 
+DEVICE MODE
+===========
+ - reg : Four register ranges as listed in the reg-names property
+ - reg-names : "ti-conf" for the TI specific registers
+	       "ep_dbics" for the standard configuration registers as
+		they are locally accessed within the DIF CS space
+	       "ep_dbics2" for the standard configuration registers as
+		they are locally accessed within the DIF CS2 space
+	       "addr_space" used to map remote RC address space
+ - interrupts : one interrupt entries must be specified for main interrupt.
+ - num-ib-windows : number of inbound address translation windows
+ - num-ob-windows : number of outbound address translation windows
+
 Optional Property:
  - gpios : Should be added if a gpio line is required to drive PERST# line
 
+NOTE: Two DT nodes may be added for each PCI controller; one for host
+mode and another for device mode. So in order for PCI to
+work in host mode, EP mode DT node should be disabled and in order to PCI to
+work in EP mode, host mode DT node should be disabled. Host mode and EP
+mode are mutually exclusive.
+
 Example:
 axi {
 	compatible = "simple-bus";