diff --git a/llvm/docs/CMake.rst b/llvm/docs/CMake.rst
--- a/llvm/docs/CMake.rst
+++ b/llvm/docs/CMake.rst
@@ -346,6 +346,12 @@
   of the machine where LLVM is being built. If you are cross-compiling, set it
   to the target architecture name.
 
+**LLVM_DEFAULT_TARGET_TRIPLE**:STRING
+  LLVM target to use for code generation when no target is explicitly specified.
+  It defaults to "host", meaning that it shall pick the architecture
+  of the machine where LLVM is being built. If you are cross-compiling, set it
+  to the target triple of your desired architecture.
+
 **LLVM_TABLEGEN**:STRING
   Full path to a native TableGen executable (usually named ``llvm-tblgen``). This is
   intended for cross-compiling: if the user sets this variable, no native