Magic ?

no, Magic is for making layouts for actual use. I need something simpler, which would let me draw a diagram to explain the floor-plan or do I just do that with generic boxes in xcircuit ? PS : I think, I am overthinking this and should just use boxes. Just wanted to know if there is a standard/widely-used software/convention for floorplans

powerpoint 😛 ?

Search for "VLSI stick diagrams". I see lots of material of how to draw them, but no suggestions about which software to use