with the correct one referenced by a pointer in the podule structure. This is
in aid of eventually making the netslot and podulebus code a little more
separate from one another.
address shift (stride). This is necessary because many podules have standard
chips with odd address-bus wiring to allow for using LDM for
bus_space_*_multi_*().
<dev/podulebus/podulebus.h> is the canonical file to include, and includes
<machine/podulebus_machdep.h>.
<arch/${MACHINE}/poudulebus/podulebus.h> remains for backward compatibility.