dm: core: add clocks node scan

Currently, all fixed-clock declared in "clocks" node in device tree
can be binded by clk_fixed_rate.c driver only if each of them have
the "simple-bus" compatible string.
This constraint has been invoked here [1].

This patch offers a solution to avoid adding "simple-bus" compatible
string to nodes that are not busses.

[1] https://patchwork.ozlabs.org/patch/558837/

Signed-off-by: Patrice Chotard <patrice.chotard@st.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

include/dm/root.h

@@ -55,6 +55,20 @@ int dm_scan_platdata(bool pre_reloc_only);
  */
 int dm_scan_fdt(const void *blob, bool pre_reloc_only);
 
+/**
+ * dm_extended_scan_fdt() - Scan the device tree and bind drivers
+ *
+ * This calls dm_scna_dft() which scans the device tree and creates a driver
+ * for each node. the top-level subnodes are examined and also all sub-nodes
+ * of "clocks" node.
+ *
+ * @blob: Pointer to device tree blob
+ * @pre_reloc_only: If true, bind only drivers with the DM_FLAG_PRE_RELOC
+ * flag. If false bind all drivers.
+ * @return 0 if OK, -ve on error
+ */
+int dm_extended_scan_fdt(const void *blob, bool pre_reloc_only);
+
 /**
  * dm_scan_other() - Scan for other devices
  *