There is an oil return line that goes from the turbo to the oil pan, this is a very common place for oil to leak. Parts are very inexpensive ($15.00) and labor charge is about an hour, maybe a bit less. It takes a minute to determine if this is the source of the leak (for an experience Volvo mechanic).
If the leak is coming from the turbo area, it could be the turbo return, or inlet, both relatively inexpensive to repair. Some seepage at the turbo is not abnormal, so unless the oil leak is excessive, it may be normal. I would suggest cleaning off the residual oil, and add dye to the system. You can then look with a black light to see exactly where the oil is coming from.