SDL: N3DS: Document the SDL_GetBasePath behaviour.

From dcfa127fd4c553db20f3e53cad9dfa7916a19b84 Mon Sep 17 00:00:00 2001
From: Pierre Wendling <[EMAIL REDACTED]>
Date: Mon, 14 Nov 2022 17:34:22 -0500
Subject: [PATCH] N3DS: Document the SDL_GetBasePath behaviour.

---
 docs/README-n3ds.md      | 1 +
 include/SDL_filesystem.h | 4 ++++
 2 files changed, 5 insertions(+)

diff --git a/docs/README-n3ds.md b/docs/README-n3ds.md
index 991eaa07fa55..66e194d0b33a 100644
--- a/docs/README-n3ds.md
+++ b/docs/README-n3ds.md
@@ -24,3 +24,4 @@ cmake --install build
 -   Currently only software rendering is supported.
 -   SDL2main should be used to ensure ROMFS is enabled.
 -   By default, the extra L2 cache and higher clock speeds of the New 2/3DS lineup are enabled. If you wish to turn it off, use `osSetSpeedupEnable(false)` in your main function.
+-   `SDL_GetBasePath` returns the romfs root instead of the executable's directory.
diff --git a/include/SDL_filesystem.h b/include/SDL_filesystem.h
index a7606bde2aa3..60f8202bed74 100644
--- a/include/SDL_filesystem.h
+++ b/include/SDL_filesystem.h
@@ -60,6 +60,10 @@ extern "C" {
  * - `parent`: the containing directory of the bundle. For example:
  *   `/Applications/SDLApp/`
  *
+ * **Nintendo 3DS Specific Functionality**: This function returns "romfs"
+ * directory of the application as it is uncommon to store resources
+ * outside the executable. As such it is not a writable directory.
+ *
  * The returned path is guaranteed to end with a path separator ('\' on
  * Windows, '/' on most other platforms).
  *