ACPI: update DSDT override documentation

Signed-off-by: Len Brown <len.brown@intel.com>

1 files changed, 15 insertions, 0 deletions

diff --git a/Documentation/acpi/dsdt-override.txt b/Documentation/acpi/dsdt-override.txt
new file mode 100644
index 000000000000..5008f256a2db
--- /dev/null
+++ b/Documentation/acpi/dsdt-override.txt
@@ -0,0 +1,15 @@
+Linux supports two methods of overriding the BIOS DSDT:
+
+CONFIG_ACPI_CUSTOM_DSDT builds the image into the kernel.
+
+CONFIG_ACPI_CUSTOM_DSDT_INITRD adds the image to the initrd.
+
+When to use these methods is described in detail on the
+Linux/ACPI home page:
+http://www.lesswatts.org/projects/acpi/overridingDSDT.php
+
+Note that if both options are used, the DSDT supplied
+by the INITRD method takes precedence.
+
+Documentation/initramfs-add-dsdt.sh is provided for convenience
+for use with the CONFIG_ACPI_CUSTOM_DSDT_INITRD method.