Platform line card driver is aware of line card I2C topology, its
responsibility is to detect line card basic hardware type, create I2C
topology (mux), connect all the necessary I2C devices, like hotswap
devices, voltage and power regulators devices, iio/a2d devices and line
card EEPROMs, creates LED instances for LED located on a line card, exposes
line card related attributes, like CPLD and FPGA versions, reset causes,
required powered through line card hwmon interface.

So this driver, and the switch driver need to talk to each other, so
the switch driver actually knows what, if anything, is in the slot.

    Andrew