[PATCH v2] docs/system: add general note about architecture and machine differences

[Linisha <linisha232@gmail.com>]

Add a note near the start of the introduction explaining that QEMU options, properties, and command lines may differ between target architectures and machine types. This helps prevent confusion when examples shown for one architecture do not work for another, such as the pflash0/pflash1 options visible in -machine help on some machines but not others.

Suggested-by: Peter Maydell <peter.maydell@linaro.org>

Buglink: https://gitlab.com/qemu-project/qemu/-/issues/3254
Signed-off-by: Linisha <linisha232@gmail.com>
---

v2: Take a different approach based on review feedback from Daniel
    Berrangé and Peter Maydell. Instead of incorrectly claiming
    pflash0/pflash1 are virt-only (they actually work on x86 pc/q35
    machines too), add a general note near the start of the introduction
    about how options, properties, and command lines may differ between
    target architectures and machine types.


 docs/system/introduction.rst | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/docs/system/introduction.rst b/docs/system/introduction.rst
index bec7291e47..8d9ef61d26 100644
--- a/docs/system/introduction.rst
+++ b/docs/system/introduction.rst
@@ -1,6 +1,15 @@
 Introduction
 ============
 
+.. note::
+   QEMU supports many different target CPU architectures and many
+   different machine types for each architecture. Options, properties,
+   and command lines that work for one architecture or machine type
+   will not necessarily work on another. The examples shown in this
+   manual are specific to the architecture and machine type being
+   demonstrated. When in doubt, consult the documentation for your
+   specific target architecture and machine type.
+
 .. _Accelerators:
 
 Virtualisation Accelerators
-- 
2.47.0.windows.1