  As one of candidate theories in the construction of regular black holes,
Einstein's gravity coupled with nonlinear electrodynamics has been a topic of
great concerns. Owing to the coupling between Einstein's gravity and nonlinear
electromagnetic fields, we need to reconsider the first law of thermodynamics,
which will lead to a new thermodynamic phase space. In such a phase space, the
equation of state accurately describes the complete phase transition process of
regular black holes. The Maxwell equal area law strictly holds when the phase
transition occurs, and the entropy obeys the Bekenstein-Hawking area formula,
which is compatible with the situation in Einstein's gravity.
