Delimit loop subdivide Hello!

I would like to make a subdivide on the upper part in order to get make the model look like it was composed of several parts as shown in the reference image.

But the loop subdivide goes over the entire model.
How could I delimit it to only the left part of the model?

In other words: I would like to get rid of the subdivide marked with a white circle in the screenshot.

Or would you start from scratch again in this case?

Thank you!
When modeling objects composed by different pieces it's sometime useful to model each piece disjoined from the other (expecially if you are planning to unwrap them).

I would rip the vertices and fill with faces the holes.



Now you can loopcut each piece individually while maintaining simple topology.