Add DeprecatedMachineType runbook

Signed-off-by: Daniel Sionov <dsionov@redhat.com>

Author: dasionov

docs/runbooks/DeprecatedMachineType.md

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+# DeprecatedMachineType
+
+## Meaning
+This alert fires when one or more Virtual Machines (VMs)
+are running with machine types that have been marked as deprecated (no longer supported).
+
+## Impact
+Running VMs on deprecated machine types can cause serious issues, including:
+Loss of certain features or degraded functionality.
+Reduced performance or unexpected behavior.
+Security vulnerabilities due to lack of ongoing support.
+Failure to restart VMs if the machine type is unsupported by the current or upgraded virt-launcher version.
+These issues can lead to service disruptions and affect workload availability during or after cluster upgrades.
+
+## Diagnosis
+This alert does **not** specify which exact machine types are deprecated on your VMs. Instead, it indicates that some VMs or VMIs are using machine types marked as deprecated by the cluster nodes.
+To identify which machine types are deprecated on your nodes, inspect the following file on each node:
+/var/lib/kubevirt-node-labeller/capabilities.xml
+
+This XML file contains the node's virtualization capabilities, including a list of guest machine types. Deprecated machine types are marked with the attribute `deprecated="yes"`.
+Example excerpt from the XML:
+```xml
+<machine maxCpus='710' deprecated='yes'>pc-q35-rhel8.6.0</machine>
+<machine maxCpus='4096'>pc-q35-rhel9.6.0</machine>
+```
+In this example, pc-q35-rhel8.6.0 is deprecated, while pc-q35-rhel9.6.0 is supported.
+
+### Next steps for admins:
+- Compare the machine types used by your VMs with the deprecated types listed in this file.
+- Plan and perform migrations of VMs using deprecated machine types to supported ones before upgrading the cluster.
+
+## Mitigation
+Update affected VMs to use a supported machine type. You can:
+- Edit VM definitions individually by modifying the spec.template.spec.domain.machine.type field.
+- Or, for a smoother and cleaner update of multiple VMs, use the kubevirt-api-lifecycle-automation tool to transition all deprecated VMs in one operation.
+This approach ensures consistent, automated migration and reduces manual errors or downtime during cluster upgrades.
+
+<!--DS: If you cannot resolve the issue, log in to the
+link:https://access.redhat.com[Customer Portal] and open a support case,
+attaching the artifacts gathered during the diagnosis procedure.-->
+<!--USstart-->
+If you cannot resolve the issue, see the following resources:
+
+- [OKD Help](https://okd.io/docs/community/help/)
+- [#virtualization Slack channel](https://kubernetes.slack.com/channels/virtualization)
+<!--USend-->