Since there is no official divisions of regions and different media houses have their own, I have made my own divisions and subdivisions. Here's what it looks like.
Chennai : Essentially comprising just Chennai district. Most other divisions keep it as 16 seats, but my guess is that the politics spills over into the entire district and not just the metropolitan area.
The other regions are described in more detail in the following posts.
[1/n]
North : The basins of the Palar and Thenpennai [and a bit of the Kaveri]. Politically dominated by the politics of the PMK and DMDK. The dry erstwhile industrial heartland.
PeriChennai - The overflow of Chennai politics. Much more urban. In some sense the ends of Chennai suburban rail. Chengalpattu, Kanchipuram and Tiruvallur.
North Arcot - Vellore, Ranipet, Tirupattur and Tiruvannamalai.
South Arcot - Villupuram, Cuddalore and Kallakurichi
Baramahal - Dharmapuri and Krishnagiri
[2/n]
Raboniel Shadowsong