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.