PCI: endpoint: Update documentation

Document the new functions pci_epc_mem_map() and pci_epc_mem_unmap().
Also add the documentation for the functions pci_epc_map_addr() and
pci_epc_unmap_addr() that were missing.

Signed-off-by: Damien Le Moal <[e-mail]>
Reviewed-by: Niklas Cassel <[e-mail]>
Reviewed-by: Manivannan Sadhasivam <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Manivannan Sadhasivam <[e-mail]>

Documentation/PCI/endpoint/pci-endpoint.rst

···
    The PCI endpoint function driver should use pci_epc_mem_free_addr() to
    free the memory space allocated using pci_epc_mem_alloc_addr().
 
+* pci_epc_map_addr()
+
+  A PCI endpoint function driver should use pci_epc_map_addr() to map to a RC
+  PCI address the CPU address of local memory obtained with
+  pci_epc_mem_alloc_addr().
+
+* pci_epc_unmap_addr()
+
+  A PCI endpoint function driver should use pci_epc_unmap_addr() to unmap the
+  CPU address of local memory mapped to a RC address with pci_epc_map_addr().
+
+* pci_epc_mem_map()
+
+  A PCI endpoint controller may impose constraints on the RC PCI addresses that
+  can be mapped. The function pci_epc_mem_map() allows endpoint function
+  drivers to allocate and map controller memory while handling such
+  constraints. This function will determine the size of the memory that must be
+  allocated with pci_epc_mem_alloc_addr() for successfully mapping a RC PCI
+  address range. This function will also indicate the size of the PCI address
+  range that was actually mapped, which can be less than the requested size, as
+  well as the offset into the allocated memory to use for accessing the mapped
+  RC PCI address range.
+
+* pci_epc_mem_unmap()
+
+  A PCI endpoint function driver can use pci_epc_mem_unmap() to unmap and free
+  controller memory that was allocated and mapped using pci_epc_mem_map().
+
+
 Other EPC APIs
 ~~~~~~~~~~~~~~