A dump of photos taken during a teardown of a SlingStudio Transmitter.
I couldn’t see any obvious serial console. The HDMI signal enters the ARM SBC through an HDMI->CSI bridge chip (also available for the Raspberry Pi, and something I’ve previously blogged about) called the TC358743XBG.
Of interest is the relatively high performance WiFi card, mounted on the carrier board via PCI-Express.