only the 3 serie c division winners qualify directly.
there's also a playoff winner who is promoted. playoff format is pretty complicated: the teams that finish at 2nd to 10th places of the 3 divisions, + the coppa italia serie c winner make the 28 playoff teams. then the playoff is played in 3 rounds: playoff for each division, national playoff, then a final four. the winner of the final four also qualifies for serie b.