What does 2 Chronicles 23:3 mean?

the whole group made a covenant with the king in God's temple. Jehoiada said to them, 'Look, the king's son is alive. He has to be king, just like God promised about David's descendants.' 2 Chronicles 23:3 - Modern Text Bible

(Jehoiada reveals Joash to the leaders and reminds them of God's promise that a descendant of David should always be king. This is about restoring God's plan.)