doc: platform-support.md: Document port

Author: hegza

src/doc/rustc/src/platform-support.md

@@ -410,5 +410,8 @@ target | std | host | notes
 [`riscv32imafc-unknown-nuttx-elf`](platform-support/nuttx.md) | * |  | RISC-V 32bit with NuttX
 [`riscv64imac-unknown-nuttx-elf`](platform-support/nuttx.md) | * |  | RISC-V 64bit with NuttX
 [`riscv64gc-unknown-nuttx-elf`](platform-support/nuttx.md) | * |  | RISC-V 64bit with NuttX
+[`riscv32e-unknown-none-elf`](platform-support/riscv32-unknown-none-elf.md) | * |  | Bare RISC-V (RV32E ISA)
+[`riscv32em-unknown-none-elf`](platform-support/riscv32-unknown-none-elf.md) | * |  | Bare RISC-V (RV32EM ISA)
+[`riscv32emc-unknown-none-elf`](platform-support/riscv32-unknown-none-elf.md) | * |  | Bare RISC-V (RV32EMC ISA)
 
 [runs on NVIDIA GPUs]: https://github.com/japaric-archived/nvptx#targets

src/doc/rustc/src/platform-support/riscv32-unknown-none-elf.md

@@ -1,12 +1,12 @@
-# `riscv32{i,im,ima,imc,imac,imafc}-unknown-none-elf`
+# `riscv32{i,im,ima,imc,imac,imafc,e,em,emc}-unknown-none-elf`
 
 **Tier: 2**
 
 Bare-metal target for RISC-V CPUs with the RV32I, RV32IM, RV32IMC, RV32IMAFC and RV32IMAC ISAs.
 
 **Tier: 3**
 
-Bare-metal target for RISC-V CPUs with the RV32IMA ISA.
+Bare-metal target for RISC-V CPUs with the RV32IMA, RV32E, RV32EM and RV32EMC ISAs.
 
 ## Target maintainers