Adam Breeden/ZDNET Follow ZDNET: Add us as a preferred source on Google. With the exception of USB and HDMI inputs, you've probably never given much thought to the ports and connections your TV offers, especially once your home theater system is set up. But the RS-232 serial port can be a valuable tool for more advanced tech users looking to create a truly custom home theater or who want total control over their smart devices.  Also:  I changed 13 settings on my TV to dramatically improve its performance - here's how With some patience and more than a little know-how, you can create a fully automated home entertainment system with timed content, simultaneous broadcasts to multiple rooms, and even diagnostic testing.   What is an RS-232 serial port, and what does it do?…