Add new maintainers

Author: Hoverbear

src/doc/rustc/src/SUMMARY.md

@@ -65,6 +65,7 @@
     - [riscv32im-risc0-zkvm-elf](platform-support/riscv32im-risc0-zkvm-elf.md)
     - [riscv32imac-unknown-xous-elf](platform-support/riscv32imac-unknown-xous-elf.md)
     - [riscv32*-unknown-none-elf](platform-support/riscv32-unknown-none-elf.md)
+    - [riscv64gc-unknown-linux-gnu](platform-support/riscv64gc-unknown-linux-gnu.md)
     - [sparc-unknown-none-elf](./platform-support/sparc-unknown-none-elf.md)
     - [*-pc-windows-gnullvm](platform-support/pc-windows-gnullvm.md)
     - [\*-nto-qnx-\*](platform-support/nto-qnx.md)

src/doc/rustc/src/platform-support/riscv64gc-unknown-linux-gnu.md

@@ -7,8 +7,10 @@ RISC-V targets using the *RV64I* base instruction set with the *G* collection of
 
 ## Target maintainers
 
--  TODO
-
+- Kito Cheng, <kito.cheng@gmail.com>, [@kito-cheng](https://github.com/kito-cheng)
+- Michael Maitland, <michaeltmaitland@gmail.com>, [@michaelmaitland](https://github.com/michaelmaitland)
+- Robin Randhawa, <robin.randhawa@sifive.com>, [@robin-randhawa-sifive](https://github.com/robin-randhawa-sifive)
+- Craig Topper, <craig.topper@sifive.com>, [@topperc](https://github.com/topperc)
 
 ## Requirements