FAT filenames referenced within EFI$CP always use a device or
    device alias name, and use backslashes as directory and filename
    delimiters.

    When referencing a directory, a trailing backslash is expected
    and must be present. If no trailing backslash is present,
    the trailing portion of the specification located after the
    final backslash is assumed to be a filename. The exception is
    CREATE/DIR which will assume a trailing backslash if not present.

    Both FAT short and long filenames are permitted, as are filenames
    containing various special characters as defined in the FAT
    specifications. FAT is case-preserving and case-blind.

    ddcu:\dir\subdir\file
    ddcu:\dir\subdir\file.ext
    ddcu:\dir\subdir\subdir2\
    "ddcu:\long name with spaces\"