Why is $Ω(H) ≤ Ω(\hat{H}) + \langle ∇Ω(\hat{H}), H − \hat{H} \rangle$ true?

Question

I read this paper, it provides a short information for majorizing function $Ω(H)$ which is log function (concave).

At before equation 4,

$Ω(\hat{H})$ denotes the value of $H$ at the current iteration. Next, since $Ω$ is concave, we can majorize it by its tangent at $Ω(H) ≤ Ω(\hat{H}) + \langle ∇Ω(\hat{H}), H − \hat{H} \rangle$

What I know is this should relate to the majorization of log function $log(θ) ≤ log(θ′) + θ/θ′ − 1$ since $Ω(H)$ is log function. But I don't understand how the term $\langle ∇Ω(\hat{H}), H − \hat{H} \rangle$ come from?