diff --git a/Documentation/powerpc/booting-without-of.txt b/Documentation/powerpc/booting-without-of.txt
index 6d5a5a0fa5e8b380b2ee478b94d3f31a79159374..a1f83f1c24c97a5e9bfaa3979dbe8c66fc7fd875 100644
--- a/Documentation/powerpc/booting-without-of.txt
+++ b/Documentation/powerpc/booting-without-of.txt
@@ -265,6 +265,9 @@ struct boot_param_header {
                                            booting on */
         /* version 3 fields below */
         u32     size_dt_strings;        /* size of the strings block */
+
+        /* version 17 fields below */
+        u32	size_dt_struct;		/* size of the DT structure block */
 };
 
    Along with the constants:
@@ -335,10 +338,13 @@ struct boot_param_header {
      to reallocate it easily at boot and free up the unused flattened
      structure after expansion. Version 16 introduces a new more
      "compact" format for the tree itself that is however not backward
-     compatible. You should always generate a structure of the highest
-     version defined at the time of your implementation. Currently
-     that is version 16, unless you explicitly aim at being backward
-     compatible.
+     compatible. Version 17 adds an additional field, size_dt_struct,
+     allowing it to be reallocated or moved more easily (this is
+     particularly useful for bootloaders which need to make
+     adjustments to a device tree based on probed information). You
+     should always generate a structure of the highest version defined
+     at the time of your implementation. Currently that is version 17,
+     unless you explicitly aim at being backward compatible.
 
    - last_comp_version
 
@@ -347,7 +353,7 @@ struct boot_param_header {
      is backward compatible with version 1 (that is, a kernel build
      for version 1 will be able to boot with a version 2 format). You
      should put a 1 in this field if you generate a device tree of
-     version 1 to 3, or 0x10 if you generate a tree of version 0x10
+     version 1 to 3, or 16 if you generate a tree of version 16 or 17
      using the new unit name format.
 
    - boot_cpuid_phys
@@ -360,6 +366,17 @@ struct boot_param_header {
      point (see further chapters for more informations on the required
      device-tree contents)
 
+   - size_dt_strings
+
+     This field only exists on version 3 and later headers.  It
+     gives the size of the "strings" section of the device tree (which
+     starts at the offset given by off_dt_strings).
+
+   - size_dt_struct
+
+     This field only exists on version 17 and later headers.  It gives
+     the size of the "structure" section of the device tree (which
+     starts at the offset given by off_dt_struct).
 
    So the typical layout of a DT block (though the various parts don't
    need to be in that order) looks like this (addresses go from top to
@@ -417,7 +434,7 @@ root node who has no parent.
 A node has 2 names. The actual node name is generally contained in a
 property of type "name" in the node property list whose value is a
 zero terminated string and is mandatory for version 1 to 3 of the
-format definition (as it is in Open Firmware). Version 0x10 makes it
+format definition (as it is in Open Firmware). Version 16 makes it
 optional as it can generate it from the unit name defined below.
 
 There is also a "unit name" that is used to differentiate nodes with
diff --git a/include/asm-powerpc/prom.h b/include/asm-powerpc/prom.h
index 1aa15e2e056e39961d51f8b65d5bad0d46ce930a..994de8ea33086dee690b96536b84c6c59a9f193a 100644
--- a/include/asm-powerpc/prom.h
+++ b/include/asm-powerpc/prom.h
@@ -59,6 +59,8 @@ struct boot_param_header
 	u32	boot_cpuid_phys;	/* Physical CPU id we're booting on */
 	/* version 3 fields below */
 	u32	dt_strings_size;	/* size of the DT strings block */
+	/* version 17 fields below */
+	u32	dt_struct_size;		/* size of the DT structure block */
 };