How to perform the upload with multiple files

I'm not used to use CI file upload but it seems you are in trouble since do_upload() seems to be made to one file only...

I would suggest:
1) Do a method to save $_FILES into another var and then try to override $_FILES with the proper structure and call do_upload on each file? Seems very clumsy but maybe it's possible to do this? I dunno...
2) Create another method similar to do_upload but prepared to receive that array of files.
3) Use another library like https://github.com/blueimp/jQuery-File-Upload