[PATCH for-9.0] docs/about: Mark the iaspc machine type as deprecated

[Igor Mammedov]

ISAPC machine was introduced 25 years ago and it's a lot of time since
such machine was around with real ISA only PC hardware practically defunct.
Also it's slowly bit-rots (for example: I was able to boot RHEL6 on RHEL9 host
in only TCG mode, while in KVM mode it hung in the middle of boot)

Rather than spending time on fixing 'the oldest' no longer tested machine type,
deprecate it so we can clean up QEMU code from legacy fixups and hopefully
make it easier to follow.

Folks who have to use ancient guest that requires ISAPC can still
use older QEMU to play with it.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
---
 docs/about/deprecated.rst | 7 +++++++
 hw/i386/pc_piix.c         | 1 +
 2 files changed, 8 insertions(+)

diff --git a/docs/about/deprecated.rst b/docs/about/deprecated.rst
index 7b548519b5..5708296991 100644
--- a/docs/about/deprecated.rst
+++ b/docs/about/deprecated.rst
@@ -226,6 +226,13 @@ These old machine types are quite neglected nowadays and 
thus might have
 various pitfalls with regards to live migration. Use a newer machine type
 instead.
 
+``isapc`` (since 9.0)
+'''''''''''''''''''''''''''''''''''''''''''''''''''''
+
+These old machine type are quite neglected nowadays and thus might have
+various pitfalls with regards to live migration. Use a newer machine type
+instead.
+
 Nios II ``10m50-ghrd`` and ``nios2-generic-nommu`` machines (since 8.2)
 '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
 
diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
index 18ba076609..96f72384dd 100644
--- a/hw/i386/pc_piix.c
+++ b/hw/i386/pc_piix.c
@@ -921,6 +921,7 @@ static void isapc_machine_options(MachineClass *m)
     m->default_nic = "ne2k_isa";
     m->default_cpu_type = X86_CPU_TYPE_NAME("486");
     m->no_parallel = !module_object_class_by_name(TYPE_ISA_PARALLEL);
+    m->deprecation_reason = "old and unattended - use a newer version instead";
 }
 
 DEFINE_PC_MACHINE(isapc, "isapc", pc_init_isa,
-- 
2.43.0