linux/Documentation/features/arch-support.txt

For generic kernel features that need architecture support, the
arch-support.txt file in each feature directory shows the arch
support matrix, for all upstream Linux architectures.

The meaning of entries in the tables is:

    | ok |  # feature supported by the architecture
    |TODO|  # feature not yet supported by the architecture
    | .. |  # feature cannot be supported by the hardware
    | N/A|  # feature doesn't apply to the architecture