Logstash.conf configuration error question

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Versions (relevant - OpenSearch/Dashboard/Server OS/Browser):
opensearchproject/logstash-oss-with-opensearch-output-plugin:8.4.0

Describe the issue:

It configures Opensearch + Logstash in Kubernetes Infra.
I want to set logstash.conf for several services.
Deployment.yaml - Changed the existing /etc/logstash.conf Path to /etc/logstash/conf.d/logstash.conf Path.
This will result in the following error and will not work:
What’s the problem?

Configuration:

# (Deployment)  Before
        volumeMounts:
        - name: logstashconfig-volume
          mountPath: /etc/logstash.conf
          readOnly: true
          subPath: logstash.conf

# (Deployment) After
        volumeMounts:
        - name: logstashconfig-volume
          mountPath: /etc/logstash/conf.d/logstash.conf
          readOnly: true
          subPath: logstash.conf

Relevant Logs or Screenshots:

[2023-03-21T01:43:40,277][INFO ][logstash.config.source.local.configpathloader] No config files found in path {:path=>"/etc/logstash.conf"}
[2023-03-21T01:43:40,282][ERROR][logstash.config.sourceloader] No configuration found in the configured sources.
[2023-03-21T01:43:40,406][INFO ][logstash.agent           ] Successfully started Logstash API endpoint {:port=>9600, :ssl_enabled=>false}
[2023-03-21T01:43:40,437][INFO ][logstash.runner          ] Logstash shut down.
[2023-03-21T01:43:40,444][FATAL][org.logstash.Logstash    ] Logstash stopped processing because of an error: (SystemExit) exit
org.jruby.exceptions.SystemExit: (SystemExit) exit
  at org.jruby.RubyKernel.exit(org/jruby/RubyKernel.java:790) ~[jruby.jar:?]
  at org.jruby.RubyKernel.exit(org/jruby/RubyKernel.java:753) ~[jruby.jar:?]
  at usr.share.logstash.lib.bootstrap.environment.<main>(/usr/share/logstash/lib/bootstrap/environment.rb:91) ~[?:?]