[lld] [lld][docs] Document two linker-script related options for lld ELF (PR #166313)

[Mingming Liu via llvm-commits]

https://github.com/mingmingl-llvm created https://github.com/llvm/llvm-project/pull/166313

This is a follow up of the discussions in https://github.com/llvm/llvm-project/pull/163497

>From 86370161c0c3a0fb5fc346e20208fc7acf35c74e Mon Sep 17 00:00:00 2001
From: mingmingl <mingmingl at google.com>
Date: Mon, 3 Nov 2025 21:52:26 -0800
Subject: [PATCH] lld docs

---
 lld/docs/ELF/linker_script.rst | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/lld/docs/ELF/linker_script.rst b/lld/docs/ELF/linker_script.rst
index c9cb47fc0553e..2946e0156583e 100644
--- a/lld/docs/ELF/linker_script.rst
+++ b/lld/docs/ELF/linker_script.rst
@@ -17,6 +17,25 @@ possible. We reserve the right to make different implementation choices where
 it is appropriate for LLD. Intentional deviations will be documented in this
 file.
 
+Linker Script Specification
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+There are two lld options related to setting the linker script,
+`--script=<file>` and `--default-script=<file>`. The usage are illustrated below.
+
+::
+
+  # This sets `--script=<file>` option under the hood.
+  lld -T linker_script.lds
+
+  # This sets `--default-script=<file>` option under the hood.
+  lld -dT linker_script.lds
+
+When both options are given, `--script=<file>` takes precedence.
+The intended use case of `--default-script` is to be used by toolchain
+configurations, and users can override the script by specifying `--script` if
+needed.
+
 Symbol assignment
 ~~~~~~~~~~~~~~~~~