There's a lot about splits here. The general idea seems to be to split the rooms in a property, as SwissPete says, into different areas so that each area has a potentially different function but the stairs between each level are shallow for easy access.
so i guess there is a staircase from the second storey on the left side leading down to the first storey above the garage and another one leading up from the first storey on the left side to the one above the garage (too complicated!). This reminds me of the house in Wide Sargasso Sea, the house which the main character grows up in had the same kind of steps everywhere, i think because it was built on an uneven surface. they didnt call it by this name though.