BB-Black Platform/miscdevice driver - device tree entry

Hello, I have written a very basic platform/miscdevice driver, but cannot work out how to add a corresponding device node in the device tree.
(I have experience with i2c drivers - so some knowledge of how to do it)

From what I gather the device entry should sit on the main bus (“simple-bus”) in the device tree, however this is not helping so far.
All attempts to add an entry into [am33xx.dtsi] so far won’t compile.

Can anyone help shed any light on this issue, or provide some pointers please?
I will be eternally grateful!