After you have upgraded to Oracle Grid Infrastructure 21c, you can install individual software patches by downloading them from My Oracle Support.

• About Individual Oracle Grid Infrastructure Patches
  Download Oracle ASM individual (one-off) patch and apply it to Oracle Grid Infrastructure using the OPatchAuto utility.
• About Oracle Grid Infrastructure Software Patch Levels
  Review this topic to understand how to apply patches for Oracle ASM and Oracle Clusterware.
• About Zero-Downtime Oracle Grid Infrastructure Patching
  Use the zero-downtime Oracle Grid Infrastructure patching method to keep your Oracle RAC database instances running and client connections active during patching.
• Patching Oracle Grid Infrastructure
  Review these topics to patch Oracle Grid Infrastructure in different stages of installation or upgrade.
• Patching and Switching Oracle Grid Infrastructure Homes
  Use switchGridHome command to switch from the current Oracle Grid Infrastructure home to the patched Oracle Grid Infrastructure home.