At my house we have two Wifi routers one's connected directly to the modem and the other is plugged in down stairs as a second network(Directly connected to the first router) Is there a way that I could make it so that I have the second router have its own network, but have one or two ports that would act as if they were directly connected to the first router? That way I can port forward to devices on the second router. Here are the information about the routers:

Router 1 - Linksys WRT54G Running stock firmware

Router 2 - Linksys E900 Running Tomato Firmware

So to summarize what I'm asking is how would I have two networks from two routers but be able to connect directly to the first router through one of the ports on the second router.

Here's a Visio Drawing of what I would like to look like