What is the significance of Act V, Scene 2

Through York's narration, we see how completely Richard and Bolingbroke's fortunes have changed. The people of London praise Bolingbroke, while Richard has dirt thrown at him.

York's belief system, that a subject is bound to obey his king without exception, which kept him loyal to Richard, now binds him to Bolingbroke. He felt badly for Richard's treatment of Bolingbroke, but he would not turn on his king even though Bolingbroke was his nephew. In this scene, we see the extreme of York's loyalty to his new king when he is willing to turn in his own son for treason, who will most likely be executed.