Eigenvalues of block diagonal matrix

I have a block-diagonal matrix of the form

$$\begin{align*} \bf{M} = \begin{bmatrix} \bf{0} & \bf{I} \\ \bf{A} & \bf{B} \end{bmatrix} \end{align*}$$
Can we say anything about the eigenvalues of $\bf{M}$ in terms the eigenvalues of the block matrices?

Here, $\bf{0}$ is a matrix of zeros and $\bf{I}$ is an identity matrix.

This is not in block upper/lower triangular form.