pmdomain: imx8mp-blk-ctrl: Error out if domains are missing in DT

This driver assumes that domain->power_dev is non-NULL in its
suspend/resume path. The assumption is valid, since all the devices that
are being looked up here should be described in DT. In case they are not
described in DT, because the DT is faulty, suspend/resume attempt would
trigger NULL pointer dereference.

To avoid this failure, check whether the power_dev assignment is not NULL
right away in probe callback and fail early if it is.

Signed-off-by: Marek Vasut <marex@denx.de>
Reviewed-by: Peng Fan <peng.fan@nxp.com>
Link: https://lore.kernel.org/r/20240119014807.268694-1-marex@denx.de
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

pmdomain: imx8m-blk-ctrl: Convert to platform remove callback returning void

The .remove() callback for a platform driver returns an int which makes
many driver authors wrongly assume it's possible to do error handling by
returning an error code. However the value returned is ignored (apart
from emitting a warning) and this typically results in resource leaks.

To improve here there is a quest to make the remove callback return
void. In the first step of this quest all drivers are converted to
.remove_new(), which already returns void. Eventually after all drivers
are converted, .remove_new() will be renamed to .remove().

Trivially convert this driver from always returning zero in the remove
callback to the void returning variant.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Link: https://lore.kernel.org/r/20231124080623.564924-5-u.kleine-koenig@pengutronix.de
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

pmdomain: Rename the genpd subsystem to pmdomain

It has been pointed out that naming a subsystem "genpd" isn't very
self-explanatory and the acronym itself that means Generic PM Domain, is
known only by a limited group of people.

In a way to improve the situation, let's rename the subsystem to pmdomain,
which ideally should indicate that this is about so called Power Domains or
"PM domains" as we often also use within the Linux Kernel terminology.

Suggested-by: Rafael J. Wysocki <rafael@kernel.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Heiko Stuebner <heiko@sntech.de>
Acked-by: Rafael J. Wysocki <rafael@kernel.org>
Acked-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20230912221127.487327-1-ulf.hansson@linaro.org