Can gtk filechooser set to be folder-restricted?
A normal filechooser will display all folder files tree starting from / (root), what I need is, to allow filechooser displaying only from /media folder only. So, the top visible folder is only /media, not everything else like /home, /usr, etc.
Thank you for all your kindly help.
Limiting directory changes isn't directly available in FileChooser, but there are a few ways:

You can define file filters (Gtk.FileFilter) but those basically filter on the file extension (or mime type).
More interesting is that, when changing the folder, a signal is emitted called 'current_folder_changed'. So, you could bind a function to that signal and take action. Mind: if you programmatically change the folder as a result of this signal, the signal will probably be called again, so you have to temporarily block the signal while doing that.
Python gtk3 filechooser restrict folder