Switch -R0 - recurse subfolders for wildcard names only
Similar to switch -r, but when used with the commands a, u, f, m will recurse subfolders only for those file masks, which include wildcard characters '*' and '?'.
This switch works only for file names. Folder names without a file name part, such as 'foldername', are not affected by -r0 and their contents is added to archive completely unless -r- switch is specified.
Example
add all *.doc files from the current folder and its subfolders and file readme.txt only from the current folder to docs.rar archive. In case of usual -r switch, WinRAR would search for readme.txt in subfolders too.
WinRAR a -r0 docs.rar *.doc readme.txt