from the sparc64 subtree, which breaks building non-sparc64 platforms
in the event the sparc64 subtree does not exist.
The problem is specific to the module, because non-module builds are
affected by the presence or absence of "device ebus" in the kernel
configuration.
PR: kern/56869
of what uart(4) is and/or is not see the initial commit log of one
of the files in sys/dev/uart (or see share/man/man4/uart.4).
Note that currently pc98 shares the MD file with i386. This needs
to change when pc98 support is fleshed-out to properly support the
various UARTs. A good example is sparc64 in this respect.
We build uart(4) as a module on all platforms. This may break
the ppc port. That depends on whether they do actually build
modules.
To use uart(4) on alpha, one must use the NO_SIO option.