Child devices need to get a regmap from a resource struct, specifically
from the MFD parent. The MFD parent has the interface to the hardware
layer, which could be I2C, SPI, PCIe, etc.

This is somewhat a hack... ideally child devices would interface with the
struct device* directly, by way of a function like
devm_get_regmap_from_resource which would be akin to
devm_get_and_ioremap_resource. A less ideal option would be to interface
directly with MFD to get a regmap from the parent.

This solution is even less ideal than both of the two suggestions, so is
intentionally left in a separate commit after the initial MFD addition.

Signed-off-by: Colin Foster <colin.foster@in-advantage.com>
---
 drivers/mfd/ocelot-core.c |  9 +++++++++
 include/soc/mscc/ocelot.h | 12 ++++++++++++
 2 files changed, 21 insertions(+)

diff --git a/drivers/mfd/ocelot-core.c b/drivers/mfd/ocelot-core.c
index a65619a8190b..09132ea52760 100644
--- a/drivers/mfd/ocelot-core.c
+++ b/drivers/mfd/ocelot-core.c

@@ -94,6 +94,15 @@ static struct regmap *ocelot_mfd_regmap_init(struct ocelot_mfd_core *core,
 	return regmap;
 }
 
+struct regmap *ocelot_mfd_get_regmap_from_resource(struct device *dev,
+						   const struct resource *res)
+{
+	struct ocelot_mfd_core *core = dev_get_drvdata(dev);
+
+	return ocelot_mfd_regmap_init(core, res);
+}
+EXPORT_SYMBOL(ocelot_mfd_get_regmap_from_resource);