[PATCH v5 3/3] Documentation/llvm: update CROSS_COMPILE inferencing

[Nick Desaulniers]

As noted by Masahiro, document how we can generally infer CROSS_COMPILE
(and the more specific details about --target and --prefix) based on
ARCH.

Suggested-by: Masahiro Yamada <masahiroy@xxxxxxxxxx>
Signed-off-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
---
 Documentation/kbuild/llvm.rst | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/Documentation/kbuild/llvm.rst b/Documentation/kbuild/llvm.rst
index b18401d2ba82..4292f0686316 100644
--- a/Documentation/kbuild/llvm.rst
+++ b/Documentation/kbuild/llvm.rst
@@ -63,6 +63,23 @@ They can be enabled individually. The full list of the parameters: ::
 Currently, the integrated assembler is disabled by default. You can pass
 ``LLVM_IAS=1`` to enable it.
 
+Omitting CROSS_COMPILE
+----------------------
+
+As explained above, ``CROSS_COMPILE`` is used to set ``--target=<triple>``.
+
+Unless ``LLVM_IAS=1`` is specified, ``CROSS_COMPILE`` is also used to derive
+``--prefix=<path>`` to search for the GNU assembler.
+
+If ``CROSS_COMPILE`` is not specified, the ``--target=<triple>`` is inferred
+from ``ARCH``.
+
+That means if you use only LLVM tools, ``CROSS_COMPILE`` becomes unnecessary.
+
+For example, to cross-compile the arm64 kernel::
+
+	ARCH=arm64 make LLVM=1 LLVM_IAS=1
+
 Supported Architectures
 -----------------------
 
-- 
2.32.0.554.ge1b32706d8-goog