x86: Add a way to add to the e820 memory table

Some boards want to reserve extra regions of memory. Add a 'chosen'
property to support this.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/doc/device-tree-bindings/chosen.txt b/doc/device-tree-bindings/chosen.txt
index d4dfc05..e5ba672 100644
--- a/doc/device-tree-bindings/chosen.txt
+++ b/doc/device-tree-bindings/chosen.txt
@@ -143,3 +143,21 @@
 node to add. The ACPI information is written in this order.
 
 If the ordering does not include all nodes, an error is generated.
+
+e820-entries
+------------
+
+This provides a way to add entries to the e820 table which tells the OS about
+the memory map. The property contains three sets of 64-bit values:
+
+   address   - Start address of region
+   size      - Size of region
+   flags     - Flags (E820_...)
+
+Example:
+
+chosen {
+	e820-entries = /bits/ 64 <
+		IOMAP_P2SB_BAR IOMAP P2SB_SIZE E820_RESERVED
+		MCH_BASE_ADDRESS     MCH_SIZE  E820_RESERVED>;
+};