Hey there!

Some IITs offer masters in arts and doctorates so you can join IIT for that. IITs don't offer bachelors degree in arts so you cannot join IIT for that. To join IIT for masters you can appear for the following exams after your undergraduate degree : IITM entrance exam for IIT Madras, IITGN M.A. entrance exam for IIT Gandhinagar and HSEE for IIT Mumbai. Hope this helps.