Disclaimer: I worked at LinkedIn. Currently, Linkedin's job classification system doesn't have open API. You can check their documentation but they won't provide access to it. So if you want to use it in our application that'll be difficult.

SOC is a good basis but our API allows you to correct for errors, synonyms, etc... That makes our approach way more robust. We plan to provide a mapping from our classification system to the SOC at a latter time.