of/fdt: introduce of_scan_flat_dt_subnodes and of_get_flat_dt_phandle

Introduce primitives for FDT parsing. These will be used for powerpc
cpufeatures node scanning, which has quite complex structure but should
be processed early.

Cc: [e-mail]
Acked-by: Rob Herring <[e-mail]>
Signed-off-by: Nicholas Piggin <[e-mail]>
Signed-off-by: Michael Ellerman <[e-mail]>

drivers/of/fdt.c

···
 }
 
 /**
+ * of_scan_flat_dt_subnodes - scan sub-nodes of a node call callback on each.
+ * @it: callback function
+ * @data: context data pointer
+ *
+ * This function is used to scan sub-nodes of a node.
+ */
+int __init of_scan_flat_dt_subnodes(unsigned long parent,
+				    int (*it)(unsigned long node,
+					      const char *uname,
+					      void *data),
+				    void *data)
+{
+	const void *blob = initial_boot_params;
+	int node;
+
+	fdt_for_each_subnode(node, blob, parent) {
+		const char *pathp;
+		int rc;
+
+		pathp = fdt_get_name(blob, node, NULL);
+		if (*pathp == '/')
+			pathp = kbasename(pathp);
+		rc = it(node, pathp, data);
+		if (rc)
+			return rc;
+	}
+	return 0;
+}
+
+/**
  * of_get_flat_dt_subnode_by_name - get the subnode by given name
  *
  * @node: the parent node
···
 int __init of_flat_dt_match(unsigned long node, const char *const *compat)
 {
 	return of_fdt_match(initial_boot_params, node, compat);
+}
+
+/**
+ * of_get_flat_dt_prop - Given a node in the flat blob, return the phandle
+ */
+uint32_t __init of_get_flat_dt_phandle(unsigned long node)
+{
+	return fdt_get_phandle(initial_boot_params, node);
 }
 
 struct fdt_scan_status {

include/linux/of_fdt.h

···
 extern int of_scan_flat_dt(int (*it)(unsigned long node, const char *uname,
 				     int depth, void *data),
 			   void *data);
+extern int of_scan_flat_dt_subnodes(unsigned long node,
+				    int (*it)(unsigned long node,
+					      const char *uname,
+					      void *data),
+				    void *data);
 extern int of_get_flat_dt_subnode_by_name(unsigned long node,
 					  const char *uname);
 extern const void *of_get_flat_dt_prop(unsigned long node, const char *name,
···
 extern int of_flat_dt_match(unsigned long node, const char *const *matches);
 extern unsigned long of_get_flat_dt_root(void);
 extern int of_get_flat_dt_size(void);
+extern uint32_t of_get_flat_dt_phandle(unsigned long node);
 
 extern int early_init_dt_scan_chosen(unsigned long node, const char *uname,
 				     int depth, void *data);