Website: https://www.mitre.org/news-insights/publication/11-strategies-world-class-cybersecurity-operations-center
This 452-page document(!) is a mammoth resource to learn about what SOCs do, how to build one, how to staff a SOC, and details on the functions it performs.
It gives you further references to read, a timeline to establish or grow a SOC, documentation, and tool references. I can’t stress how valuable this resource is to learn more about a SOC, cybersecurity in general, or if you are a SOC analyst.