For a typical driver, I would add a series termination resistor to terminate the line.
But what would be the correct way to terminate when a transistor is used to level shift a 3.3V/5V signal to some arbitrary voltage ?
Consider a simple circuit, V1 is some higher voltage to which I am switching to. Could be 12V, 15V, or 30V. R2 is a pullup. The pullup value would be most likely greater than Z0, otherwise, the power loss at high frequencies could be pretty big. 30V and say R2 is 50 ohms, thats 18W, when the transistor turns on and 600mA through it. So I would imagine that that the pullup would be much higher to combat that.
I've never seen in any book, app note, or any reference that speaks about this.