So I've looked into the TC358870XBG and it seems that 2 I2C pins, 1 reset pin, 1 clock pin and an INT pin is needed. One probably could make a circuit that generated the clock instead of the MCU, but a free pin is cheaper than that. 

The main issue I was having was the INT pin, since it seems that it acts as a strapping pin (as in it sets the I2C address on reset) and an interrupt pin. I didn't have the 3 - 4 spare pins for interrupts, and I was thinking of seeing if I could connect the BLDC controller to a 3:8 decoder to free up some pins, but then I remembered that a single Tetrinsic doesn't have to control it all. Thus, instead of each Tetrinsic having (or trying to have) a

• MIPI_RESET
• MIPI_INT[0-3]
• CLK_MIPI
• ADDRESSABLE_RGB
• DAC_SD

I can have 2 Tetrinsics focus on 2 of the pins. As long as 4 Tetrinsics support all the features, it's ok.