How to embed a clock oscillator inside a digital block? Specifically, how is this defined for Synopsys DC?
What I have done in my designs is

create_clock -name CLOCK_INT -period 47 [get_pins OSCILLATOR_INSTANCE/CLKPORT]

If memory serves me correctly (and check the DC guide to be sure) the target of the create_clock command needs to be a "pin object" and not just the pin name. The command get_pins returns a pin object, and if you specify the exact pin as the argument, it doesn't require any additional filtering.