Who has the final say or is in charge hierarchically in your company, product ppl/head/department or the cto/vp r&d?

Pls mention company size small/medium/large

Just want to know what's more accepted in the industry.

To clearify, for example, do most projects ideas get created by the managment and brought to RnD director who then assigns the product team to create the full specifications.
Or, is the idea first reaches product departmnet and then RnD department just gets the specifications and starts work.