hw/mips: Mark the "mipssim" machine as deprecated

We are not aware of anybody still using this machine, support for it
has been withdrawn from the Linux kernel (i.e. there also won't be
any future development anymore), and we are not aware of any binaries
online that could be used for regression testing to avoid that the
machine bitrots ... thus let's mark it as deprecated now.

Signed-off-by: Thomas Huth <thuth@redhat.com>
Acked-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20250121103655.1285596-1-thuth@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>

docs/about/deprecated.rst

@@ -292,6 +292,19 @@ Big-Endian variants of MicroBlaze ``petalogix-ml605`` and ``xlnx-zynqmp-pmu`` ma
 Both ``petalogix-ml605`` and ``xlnx-zynqmp-pmu`` were added for little endian
 CPUs. Big endian support is not tested.
 
+Mips ``mipssim`` machine (since 10.0)
+'''''''''''''''''''''''''''''''''''''
+
+Linux dropped support for this virtual machine type in kernel v3.7, and
+there does not seem to be anybody around who is still using this board
+in QEMU: Most former MIPS-related people are working on other architectures
+in their everyday job nowadays, and we are also not aware of anybody still
+using old binaries with this board (i.e. there is also no binary available
+online to check that this board did not completely bitrot yet). It is
+recommended to use another MIPS machine for future MIPS code development
+instead.
+
+
 Backend options
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