I own Suzuki Swift diesel, the engine is 1248cc Fiat sourced diesel engine with a small FGT turbocharger. I overfilled the engine with about 1/2 litre too much engine oil and drove at high speeds on highway for about 80 kms. Could this cause damage to the turbo or engine. I have drained the excess oil. The oil capacity is 3.1 L and I poured in 3.6 L.
It would be hard to give you a definitive answer without access to the engineering data for the engine (unless there are folks out there with real-life experience), but it seems quite unlikely.
Half of a litre isn't much oil and it is well within the range of "reasonable" mistakes: accidental overfilling, filling to spec without changing the oil filter, adding quarts instead of litre, etc. So, I would expect the design of the engine to allow for this.
Consider also that, 1/2 of a litre spread over the area of your oil pan won't result in much of an increase in the oil level. I'd guess that it would be less than the amount of sloshing from side-to-side during heavy braking or cornering.
All-in-all I think it is highly unlikely that you've done any damage – especially since you're not seeing any change in the engine's behavior.