RZ/{G2L, V2L, G3S}-based CPG versions have support for saving extra
power when clocks are disabled by activating module standby.  This is
done through MSTOP-specific registers that are part of CPG.  Each
individual module has one or more bits associated with one MSTOP
register (see table "Registers for Module Standby Mode" from HW
manuals).  Hardware manual associates modules' clocks with one or more
MSTOP bits.  There are 3 mappings available (identified by researching
RZ/G2L, RZ/G3S, RZ/V2L HW manuals):

case 1: N clocks mapped to N MSTOP bits (with N={0, ..., X})
case 2: N clocks mapped to 1 MSTOP bit  (with N={0, ..., X})
case 3: N clocks mapped to M MSTOP bits (with N={0, ..., X}, M={0, ..., Y})

Case 3 has been currently identified on RZ/V2L for the VCPL4 module.

To cover all three cases, the individual platform drivers will provide
the clock driver with MSTOP register offsets and associated bits in this
register as a bitmask, and the clock driver will apply this bitmask to
the proper MSTOP register.

The MSTOP support was implemented through power domains.
Platform-specific clock drivers will register an array of type struct
rzg2l_cpg_pm_domain_init_data, which will be used to instantiate
properly the power domains.
Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
Link: https://lore.kernel.org/r/20240422105355.1622177-7-claudiu.beznea.uj@bp.renesas.comSigned-off-by: Geert Uytterhoeven <geert+renesas@glider.be>