“ Mortgage interest. Many U.S. homeowners can deduct what they paid in mortgage interest when they file their taxes each year. (The rule is that you can deduct a home mortgage's interest on the first $750,000 of debt, or $375,000 if you're married and filing separately.”
The mortgage interest deduction is "qualified residence interest" in the statute. 26 USC §163(h)(3) allows deduction of interest "with respect to any qualified residence of the taxpayer."
"Qualified residence" is itself defined at 26 USC §163(h)(4)(A)(i) as the taxpayer's "principal residence" and "1 other residence of the taxpayer."
