Act 2 scene 3
Northumberland flatters Bolingbroke every bit a much as Bushy, Bagot, or Green flattered Richard. When in the next speech Northumberland introduces us to Harry Percy, Shakespeare is anticipating the character of Hotspur that Bolingbroke as Henry IV admires so much more than his own son, Prince Hal. We never hear of Prince Hal in this play, but since Richard takes Aumerle with him to Ireland and it was customary for Kings to take, almost as hostages, the sons of important nobles, and undoubtedly, Richard would have taken with him Bolingbroke's son Henry.
In the course of several lines, Bolingbroke mentions his state of being without funds, mentioning that he has been disenfranchised and has nothing with which to promise Northumberland, Ross, or Willoughby any reward or favor for their support. He refers to his "fortune" and in a speech later "all my treasury." When he becomes king, he has not promised them any particular reward for their support. And, in fact, in Henry IV part 1, Henry IV (Bolingbroke) will be engaged in a civil war against Northumberland and his son, Harry Percy or Hotspur, because they did not feel he valued or rewarded them enough for their aid in getting the throne for Henry IV.
When Bolingbroke is addressed by his former title, Hereford, he says he will not answer unless he gets his rightful title. This is a statement of his intentions for coming back to England. It may not be his only motivation, but it is perceived to be a legitimate one by many.
Bolingbroke uses the same argument that York had used as an argument to Richard, that the law of primogeniture is the basis for all inheritance, even Richard's claim to the throne. But also like Gaunt, York tries to redress the wrongs within the power structure which exists, not to rebel against it, certainly not be force of arms.
Bushy, Bagot, and Green are refered to as the caterpillars, the insects which are pests eating away at the garden of England. This foreshadows the Gardener scene (Act 3 scene 4), in which Richard is associated with a poor gardener who has let his garden (England) fall into disrepair.