First I ask this because of similar (mathematical) structures of these relativistic wave equations.
In addition, by quantization definitely I don't mean a canonical (or second) quantization. Moreover, if we also accept that a 1-spin single photon is described quantum mechanically by Maxwell equations, similar to Dirac equation which quantum mechanically describe a single electron (or any single 1/2-spin particle). In this regard, a more explicit discussion could be found in this page: What equation describes the wavefunction of a single photon? .