Definition of an SME in the PE context

Hello SBTi FI guidance brain trust! Thank you for your hard work in keeping us all educated about this new guidance. We are working with a PE client that has varying degrees of ownership in its portfolio companies (ranging from 1% to 100%). The question is whether the SME streamlined validation route is available to any of its portfolio companies. In other words, is a “subsidiary” defined in the financial reporting sense of the word (>50% ownership), or does it mean any company in which the fund owns an equity interest? Thank you!