of: property: Add device link support for "iommu-map"

Commit 8e12257 ("of: property: Add device link support for iommus,
mboxes and io-channels") added device link support for IOMMU linkages
described using the "iommus" property. For PCI devices, this property
is not present and instead the "iommu-map" property is used on the host
bridge node to map the endpoint RequesterIDs to their corresponding
IOMMU instance.

Add support for "iommu-map" to the device link supplier bindings so that
probing of PCI devices can be deferred until after the IOMMU is
available.

Cc: Rob Herring <robh@kernel.org>
Cc: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>
Acked-by: Saravana Kannan <saravanak@google.com>
Link: https://lore.kernel.org/r/20191120190028.4722-1-will@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/of/property.c

@@ -1190,10 +1190,20 @@ DEFINE_SIMPLE_PROP(mboxes, "mboxes", "#mbox-cells")
 DEFINE_SIMPLE_PROP(io_channels, "io-channel", "#io-channel-cells")
 DEFINE_SUFFIX_PROP(regulators, "-supply", NULL)
 
+static struct device_node *parse_iommu_maps(struct device_node *np,
+					    const char *prop_name, int index)
+{
+	if (strcmp(prop_name, "iommu-map"))
+		return NULL;
+
+	return of_parse_phandle(np, prop_name, (index * 4) + 1);
+}
+
 static const struct supplier_bindings of_supplier_bindings[] = {
 	{ .parse_prop = parse_clocks, },
 	{ .parse_prop = parse_interconnects, },
 	{ .parse_prop = parse_iommus, },
+	{ .parse_prop = parse_iommu_maps, },
 	{ .parse_prop = parse_mboxes, },
 	{ .parse_prop = parse_io_channels, },
 	{ .parse_prop = parse_regulators, },