PCI Endpoint Function Device

This describes the generic bindings to be used when a device has to be
exposed to the remote host over PCIe. The device could be an actual
peripheral in the platform or a virtual device created by the software.

epcs : phandle to the endpoint controller device
epc-names : the names of the endpoint controller device corresponding
	    to the EPCs present in the *epcs* phandle
vendor-id: used to identify device manufacturer
device-id: used to identify a particular device
baseclass-code: used to classify the type of function the device performs
subclass-code: used to identify more specifically the function of the device
subsys-vendor-id: used to identify vendor of the add-in card or subsystem
subsys-id: used to specify an id that is specific to a vendor

Example:
Following is an example of NTB device exposed to the remote host.

ntb {
	compatible = "pci-epf-ntb";
	epcs = <&pcie0_ep>, <&pcie1_ep>;
	epc-names = "primary", "secondary";
	vendor-id = /bits/ 16 <0x104c>;
	device-id = /bits/ 16 <0xb00d>;
	num-mws = <4>;
	mws-size = <0x100000>, <0x100000>, <0x100000>, <0x100000>;
};
