Perhaps the poster meant cultural North India, which (in my experience) is only contrasted with cultural South India, which is comprised of the states in which Dravidian languages are spoken by a majority, namely: Kerala, Tamil Nadu, Karnataka, AP, and Telangana.
You have my apologies. We often joke that anything northern than Bangalore is North India!
Well then Chennai is North India!! A lot of people don't realize that Bangalore is actually south of Chennai.
I think when people say "North India" what they typically mean is the areas that speak Indo-Aryan languages (as opposed to Dravidian ones).