The future support for applying a addon on a base device-tree needs to
get an offset to a property based on the node offset and the
property name.

Several function exists to get a property but none of them allows to
get the property offset.

Fill the lack and introduce fdt_getprop_offset()

Signed-off-by: Herve Codina <herve.codina@bootlin.com>
---
 libfdt/fdt_ro.c          | 12 ++++++++++++
 libfdt/libfdt_internal.h |  2 ++
 2 files changed, 14 insertions(+)

diff --git a/libfdt/fdt_ro.c b/libfdt/fdt_ro.c
index 63494fb..29692f9 100644
--- a/libfdt/fdt_ro.c
+++ b/libfdt/fdt_ro.c
@@ -508,6 +508,18 @@ const void *fdt_getprop(const void *fdt, int nodeoffset,
 	return fdt_getprop_namelen(fdt, nodeoffset, name, strlen(name), lenp);
 }
 
+int fdt_getprop_offset(const void *fdt, int nodeoffset, const char *name)
+{
+	const struct fdt_property *prop;
+	int lenp, offset;
+
+	prop = fdt_get_property_namelen_(fdt, nodeoffset, name, strlen(name),
+					 &lenp, &offset);
+	if (!prop)
+		return lenp;
+	return offset;
+}
+
 uint32_t fdt_get_phandle(const void *fdt, int nodeoffset)
 {
 	const fdt32_t *php;
diff --git a/libfdt/libfdt_internal.h b/libfdt/libfdt_internal.h
index d80d218..499e821 100644
--- a/libfdt/libfdt_internal.h
+++ b/libfdt/libfdt_internal.h
@@ -24,6 +24,8 @@ int32_t fdt_ro_probe_(const void *fdt);
 int fdt_check_node_offset_(const void *fdt, int offset);
 int fdt_check_prop_offset_(const void *fdt, int offset);
 
+int fdt_getprop_offset(const void *fdt, int nodeoffset, const char *name);
+
 const char *fdt_find_string_len_(const char *strtab, int tabsize, const char *s,
 				 int s_len);
 static inline const char *fdt_find_string_(const char *strtab, int tabsize,
-- 
2.52.0