tramp-foreign-file-name-handler-alist

tramp-foreign-file-name-handler-alist is a variable defined in `tramp.el'.
Its value is

((tramp-smb-file-name-p . tramp-smb-file-name-handler)
 (tramp-gvfs-file-name-p . tramp-gvfs-file-name-handler)
 (tramp-ftp-file-name-p . tramp-ftp-file-name-handler)
 (tramp-adb-file-name-p . tramp-adb-file-name-handler)
 (identity . tramp-sh-file-name-handler))

Documentation:
Alist of elements (FUNCTION . HANDLER) for foreign methods handled specially.
If (FUNCTION FILENAME) returns non-nil, then all I/O on that file is done by
calling HANDLER.