GEO_IA2015 (V101_IA2015) indicates the region of India where the respondent was interviewed. DHS units in the 2015 India survey are equivalent to states, with the capital as its own region.
Other sample years have their own sample-specific geography variables. There is also an integrated variable, GEO_IA1992_2015, that provides spatially consistent units over time. Greater geographic detail for the 2015 India sample can be found in GEOALT_IA2015 (districts).
A GIS map for GEO_IA2015 (in shapefile format) can be downloaded from the DHS Program Spatial Data Repository [URL omitted from DDI.] Boundaries page.