Since commit 1517126fda ("ARM: uniphier: select DM_ETH"), DM-based
drivers/net/smc911x.c is compiled, but it is never probed because the
parent node lacks the DM-based driver.
I need a skeleton driver to populate child devices (but the next commit
will move more hardware settings to the this driver).
I put this to drivers/bus/uniphier-system-bus.c because this is the
same path as the driver in Linux kernel.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>