dtoc: Add a 64-bit type and a way to convert cells into 64 bits

When dealing with multi-cell values we need a type that can hold this
value. Add this and a function to process it from a list of cell values.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Tested-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Tested-by: Kever Yang <kever.yang@rock-chips.com>

tools/dtoc/fdt_util.py

@@ -29,6 +29,20 @@ def fdt32_to_cpu(val):
         val = val.encode('raw_unicode_escape')
     return struct.unpack('>I', val)[0]
 
+def fdt_cells_to_cpu(val, cells):
+    """Convert one or two cells to a long integer
+
+    Args:
+        Value to convert (array of one or more 4-character strings)
+
+    Return:
+        A native-endian long value
+    """
+    out = long(fdt32_to_cpu(val[0]))
+    if cells == 2:
+        out = out << 32 | fdt32_to_cpu(val[1])
+    return out
+
 def EnsureCompiled(fname):
     """Compile an fdt .dts source file into a .dtb binary blob if needed.