From: Graeme Gregory <redacted>

Add documentation for the guidelines of how to use ACPI
on ARM64.

Reviewed-by: Suravee Suthikulpanit <Suravee.Suthikulpanit@amd.com>
Reviewed-by: Yi Li <redacted>
Reviewed-by: Mark Langsdorf <redacted>
Reviewed-by: Ashwin Chaugule <redacted>
Acked-by: Robert Richter <redacted>
Signed-off-by: Graeme Gregory <redacted>
Signed-off-by: Al Stone <redacted>
Signed-off-by: Hanjun Guo <redacted>
---
 Documentation/arm64/arm-acpi.txt | 506 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 506 insertions(+)
 create mode 100644 Documentation/arm64/arm-acpi.txt

diff --git a/Documentation/arm64/arm-acpi.txt b/Documentation/arm64/arm-acpi.txt
new file mode 100644
index 0000000..24cf832
--- /dev/null
+++ b/Documentation/arm64/arm-acpi.txt

@@ -0,0 +1,506 @@
+ACPI on ARMv8 Servers
+---------------------
+ACPI can be used for ARMv8 general purpose servers designed to follow
+the ARM SBSA (Server Base System Architecture) [0] and SBBR (Server
+Base Boot Requirements) [1] specifications.  Please note that the SBBR
+can be retrieved simply by visiting [1], but the SBSA is currently only
+available to those with an ARM login due to ARM IP licensing concerns.
+
+The ARMv8 kernel implements the reduced hardware model of ACPI version
+5.1 or later.  Links to the specification and all external documents
+it refers to are managed by the UEFI Forum.  The specification is
+available at http://www.uefi.org/specifications and documents referenced
+by the specification can be found via http://www.uefi.org/acpi.
+
+If an ARMv8 system does not meet the requirements of the SBSA and SBBR,
+or cannot be described using the mechanisms defined in the required ACPI
+specifications, then ACPI may not be a good fit for the hardware.
+
+While the documents mentioned above set out the requirements for building
+industry-standard ARMv8 servers, they also apply to more than one operating
+system.  The purpose of this document is to describe the interaction between
+ACPI and Linux only, on an ARMv8 system -- that is, what Linux expects of
+ACPI and what ACPI can expect of Linux.
+
+