Existing userspace protection domain mapper implementation has several
issue. It doesn't play well with CONFIG_EXTRA_FIRMWARE, it doesn't
reread JSON files if firmware location is changed (or if firmware was
not available at the time pd-mapper was started but the corresponding
directory is mounted later), etc.

Provide in-kernel service implementing protection domain mapping
required to work with several services, which are provided by the DSP
firmware.

This module is loaded automatically by the remoteproc drivers when
necessary via the symbol dependency. It uses a root node to match a
protection domains map for a particular board. It is not possible to
implement it as a 'driver' as there is no corresponding device.
Tested-by: Steev Klimaszewski <steev@kali.org>
Tested-by: Alexey Minnekhanov <alexeymin@postmarketos.org>
Reviewed-by: Chris Lew <quic_clew@quicinc.com>
Tested-by: Neil Armstrong <neil.armstrong@linaro.org> # on SM8550-QRD
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://lore.kernel.org/r/20240622-qcom-pd-mapper-v9-4-a84ee3591c8e@linaro.org
[bjorn: include linux/slab.h]
Signed-off-by: Bjorn Andersson <andersson@kernel.org>