# How to decompose this two-qubit unitary matrix to the standard gate set?

I have read some of the other decomposition questions here however still don't understand how to do it manually. The matrix I wish to decompose is the following for 2 qubits:

$$M=\frac{1}{\sqrt2}\begin{bmatrix} 1 & 0 & 0& i\\ 0 & 1& i & 0\\ 0 & i & 1 & 0\\ i & 0& 0 & 1 \end{bmatrix}$$

I have used the Qiskit circuit decompose to find that it corresponds to the following image, but I don't understand how that was done.

Also Qiskit is only able to decompose for up to 2 qubits. My application for the matrix expands beyond 2 qubits and I would also like to know how to decompose for more.

Any help on the step by step process of decomposition would be appreciated as well as any insight on multiple qubit decomposition :)