I know I'm late to the party and although many have shared very interesting links to guidelines and documentation, I think we're missing the point in the answers IMHO.
Adapting the layout and design to large screens TVs is not the responsibility of design, CSS, HTML, RWD, browser engines, HIG or any of those things.
The way I see it, adapting your website for TV browsers is the responsibility of Content Architecture, Content Strategy and Interaction Design.
This means that the content used in the website may not necessarily be suitable for a TV experience not only because of the physical implications (larger distance from device for example) but mostly because the interactions very well happens mostly with TV remote controls rather than touchscreens or mouse/keyboard combinations (although you can connect them via Blue Tooth, but we know users rarely change any defaults), and this is where Interaction Design can shine.
RWD techniques work just fine and I haven't had to come up with anything magical during implementation to be able to see my work display just fine in my 55" screen.