image: Export fit_conf_get_prop_node()

This function will be needed by signature checking code, so export it,
and also add docs.

Signed-off-by: Simon Glass <sjg@chromium.org>

common/image-fit.c

@@ -1308,7 +1308,7 @@ int fit_conf_get_node(const void *fit, const char *conf_uname)
 	return noffset;
 }
 
-static int __fit_conf_get_prop_node(const void *fit, int noffset,
+int fit_conf_get_prop_node(const void *fit, int noffset,
 		const char *prop_name)
 {
 	char *uname;
@@ -1338,7 +1338,7 @@ static int __fit_conf_get_prop_node(const void *fit, int noffset,
  */
 int fit_conf_get_kernel_node(const void *fit, int noffset)
 {
-	return __fit_conf_get_prop_node(fit, noffset, FIT_KERNEL_PROP);
+	return fit_conf_get_prop_node(fit, noffset, FIT_KERNEL_PROP);
 }
 
 /**
@@ -1357,7 +1357,7 @@ int fit_conf_get_kernel_node(const void *fit, int noffset)
  */
 int fit_conf_get_ramdisk_node(const void *fit, int noffset)
 {
-	return __fit_conf_get_prop_node(fit, noffset, FIT_RAMDISK_PROP);
+	return fit_conf_get_prop_node(fit, noffset, FIT_RAMDISK_PROP);
 }
 
 /**
@@ -1376,7 +1376,7 @@ int fit_conf_get_ramdisk_node(const void *fit, int noffset)
  */
 int fit_conf_get_fdt_node(const void *fit, int noffset)
 {
-	return __fit_conf_get_prop_node(fit, noffset, FIT_FDT_PROP);
+	return fit_conf_get_prop_node(fit, noffset, FIT_FDT_PROP);
 }
 
 /**

include/image.h

@@ -631,6 +631,20 @@ int fit_conf_get_kernel_node(const void *fit, int noffset);
 int fit_conf_get_ramdisk_node(const void *fit, int noffset);
 int fit_conf_get_fdt_node(const void *fit, int noffset);
 
+/**
+ * fit_conf_get_prop_node() - Get node refered to by a configuration
+ * @fit:	FIT to check
+ * @noffset:	Offset of conf@xxx node to check
+ * @prop_name:	Property to read from the conf node
+ *
+ * The conf@ nodes contain references to other nodes, using properties
+ * like 'kernel = "kernel@1"'. Given such a property name (e.g. "kernel"),
+ * return the offset of the node referred to (e.g. offset of node
+ * "/images/kernel@1".
+ */
+int fit_conf_get_prop_node(const void *fit, int noffset,
+		const char *prop_name);
+
 void fit_conf_print(const void *fit, int noffset, const char *p);
 
 int fit_check_ramdisk(const void *fit, int os_noffset,