I would think the goal would be a FLOSS ACPI test-suite that is written against the 980 pages long ACPI spec which validates the firmware, which can be run by the ARM hardware developers. Ideally, there should also be a corresponding FLOSS ACPI test-suite that simulates the hardware/firmware which validstes the OS (Linux). And when properly written, the suites can be run against each other to develop and validate the tests. If either the OS or firmware take actions undefined in the ACPI spec, an error would be reported. Is this painful, difficult, and time-consuming? Yes. Can it be split into smaller work units and distributed among a large team? Yes.