If you don't rent the home out, report the mortgage interest on the Mortgage Interest line in the Your Home section of TurboTax. Just click on "Add another Lender" if you've already entered mortgage interest on your primary home.
If you do rent out the home, report the mortgage interest that covers the rental time period as a rental expense on Schedule E..
**Answers are correct to the best of my ability but do not constitute tax or legal advice.