relnotes: add notes about updating ESP

Add notes about updating the ESP now that boot1.efifat has gone away.

website/content/en/releases/13.0R/relnotes.adoc

@@ -50,6 +50,12 @@ Source-based upgrades (those based on recompiling the FreeBSD base system from s
 Upgrading FreeBSD should only be attempted after backing up _all_ data and configuration files.
 ====
 
+[IMPORTANT]
+====
+Updating UEFI ESP partitions (the partition the firmware boots from) has changed.
+See <<boot>> for important details.
+====
+
 [[security-errata]]
 == Security and Errata
 
@@ -191,10 +197,18 @@ This section covers the boot loader, boot menu, and other boot-related changes.
 
 The {{< manpage "efibootmgr" "8" >}} utility now supports the `-b` flag, which lets users specify by bootnum as an index. gitref:a2581e80212[repository=src] {{< sponsored "Netflix" >}}
 
-The {{< manpage "efibootmgr" "8" >}} utility now supports the `-E` flag, which lets users query which EFI System Partition was used to boot the system. gitref:1cdb8eb8fe1[repository=src]
+The {{< manpage "efibootmgr" "8" >}} utility now supports the `-E` flag, which lets users query which EFI System Partition was used to boot the system. gitref:1cdb8eb8fe1[repository=src] {{< sponsored "Netflix" >}}
 
 The {{< manpage "efibootmgr" "8" >}} utility now supports the `-f` and `-F` flags, which lets users tell the system to boot to the UEFI user interface or not. gitref:83c4237258d[repository=src] {{< sponsored "Ampere Computing, Inc." >}}
 
+Prior releases had a complete ms-dos formatted filesystem packaged into boot1.efifat.
+Older versions of FreeBSD installed this filesystem image into a raw partition.
+However, uses of the ESP have proliferated, making this inflexible approach no longer desirable.
+Users have varied needs for the size of this partition, and multiple booting setups require more detailed access.
+To update old ESP partitions, users should stop using the {{< manpage "gpart" "8" >}} utility.
+Instead, ESP partitions should be mounted as MS-DOS filesystems as [.filename]#/boot/efi#, and [.filename]#/boot/loader.efi# should be copied to [.filename]#/boot/efi/efi/boot/bootx64.efi# if the default setup is use.
+If the {{< manpage "efibootmgr" "8" >}} utility is used to customize the boot environment, this file should be copied to the location set with the `-l` flag.
+
 [[boot-loader]]
 === Boot Loader Changes
 
@@ -317,7 +331,7 @@ Starting with FreeBSD-13.0, the default `CPUTYPE` for the i386 architecture will
 
 This means that, by default, binaries produced will require a 686-class CPU, including but not limited to binaries provided by the FreeBSD Release Engineering team. FreeBSD 13.0 will continue to support older CPUs, however users needing this functionality will need to build their own releases for official support.
 
-As the primary use for i486 and i586 CPUs is generally in the embedded market, the general end-user impact is expected to be minimal, as new hardware with these CPU types has long faded, and much of the deployed base of such systems is nearing retirement age, statistically.
+As the embedded market is the primary user of cores based on i486 and i565, end-user impact is expected to be minimal. Both server and desktop machines based on these CPU types are generally over 20 years old and have been retired or are too resource poor to make FreeBSD 13.0 an attractive upgrade.
 
 There were several factors taken into account for this change. For example, i486 does not have 64-bit atomics, and while they can be emulated in the kernel, they cannot be emulated in the userland. Additionally, the 32-bit amd64 libraries have been i686 since their inception.