The Boot and Runtime Services (BRS) specification provides the software requirements for system vendors and Operating System Vendors (OSVs) to interoperate with one another by providing expectations for the Operating System (OS) to utilize in acts of device discovery, system management, and other rich operations provided in this specification.
See the title. RSCV0003 is defined in a table in Section 6.2, "RVI-specific ACPI IDs".