It would be nice to use the same name for the OpenCores project and the
device tree identifier, and since "opencores" is already in the name,
the "oc_" bit is superfluous anyway. I'd suggest "opencores,tiny-spi"
in order to match your OpenCores project name.
Versioning of OpenCores cores is not sorted yet. In order to avoid
clashing with the versioning/naming scheme that's decided on, please
just use a neutral version number for now (especially as your core is so
new). e.g. "opencores,tiny-spi-0"