I think I know what you mean, but the layout of your garage is unknown. In my last garage I had the motion detector light on a switch, and I just left it on all the time. I could use the switch if necessary, but I could have wired the light directly.
If you are asking about the run, then you'll need to start with the incoming circuit and pigtail the wires in a junction box so that you can feed the two devices (light, garage door opener). If you wire the light directly then it will always be on; or, you can work a switch into that branch to control the light. Can you use sheathed electrical cable or is conduit required? I'm near Chicago, so it is all conduit here.
The biggest part of all this is that you need access to a junction box so that you can add two branches (using armored cable, sheathed electrical cable, or EMT -- whatever is most appropriate). I assume the opener and light are in different directions, hence the two branches.
For the garage door opener, just run your circuit to an outlet box within reach of the cord.