Scott Wilkinson recently did an article on how soundbars have the design flaw of using only a single HDMI port. But what if you have multiple HDMI devices you want to connect? Scott was reviewing an LG Atmos Soundbar, when he discovered the drawback. Looking around, he discovered the same problem with other soundbars as well. Leo says you can use Optical, and that makes sense. But Scott says the optical output is limited and doesn't support Dolby Atmos. The only thing that carries the Atmos bitstream is HDMI.
You could connect an HDMI cable to your TV IN, if it has a port that supports ARC, or audio return channel, and then back to the soundbar. It will work. Scott says if you're using a soundbar, you're not using an AV receiver. So the Soundbar should be designed with multiple HDMI input, especially for higher priced soundbars.