The Schrodinger equation for quantisation of light? Why not with the Dirac equation? Light is a born relativistic. However, when we quantise the electromagnetic wave, we start with the time-independent Schrodinger equation, which is a non-relativistic equation. Why is this fine? 
Wouldn't it more make sense if we use the Dirac equation for the quantisation of light? or do I misunderstand the physics of light with respect to the quantisation? 
 A: Light obeys Maxwell's equations.  So when we quantize light, the typical starting point is the Maxwell Lagrangian:
$$\mathscr{L} = \frac{1}{4}F^{ab}F_{ab}$$
where 
$$F_{ab} = \partial_{a}A_{b} - \partial_{b}A_{a}$$
where $A_{a}$ is the 4-dimensional vector potential $(\phi, {\vec A})$ such that ${\vec E} = -{\vec \nabla}\phi$ and ${\vec B} = {\vec \nabla} \times {\vec A}$.  
Taking the variation of the action with respect to $A_{a}$ gives the equation of motion:
$$0 = \nabla_{b}F^{ba}$$
which can be shown to be equivalent to Maxwell's equations in vacuum.
Doing a proper job of quantizing the above lagrangian requires several non-trivial tricks in quantum field theory to handle the fact that the Maxwell theory is a gauge theory and its evolution contains a constraint (this means that the naïve Hamiltonian is zero, and a "normal" Legendre transform won't just simply work).  These technical issues CAN be resolved, but typically, students are expected to have the quantization of the Klein-Gordon and Dirac fields under their belt before they do so.
Neither the Klein-Gordon nor the Dirac equations are appropriate, because photons have spin 1.
