CONFIG_RISCV is not available for thedefaultarchitecture x86.
Result is shown for architecture riscv

CONFIG_RISCV (not configurable)

configname: CONFIG_RISCV

Linux Kernel Configuration
└─>RISCV
In linux kernel since version 3.10 (release Date: 2013-06-30)  
selects
CONFIG_ARCH_CLOCKSOURCE_INIT
CONFIG_ARCH_HAS_BINFMT_FLAT
CONFIG_ARCH_HAS_DEBUG_VIRTUAL
CONFIG_ARCH_HAS_DEBUG_WX
CONFIG_ARCH_HAS_GCOV_PROFILE_ALL
CONFIG_ARCH_HAS_GIGANTIC_PAGE
CONFIG_ARCH_HAS_MMIOWB
CONFIG_ARCH_HAS_PTE_SPECIAL
CONFIG_ARCH_HAS_SET_DIRECT_MAP
CONFIG_ARCH_HAS_SET_MEMORY
CONFIG_ARCH_HAS_STRICT_KERNEL_RWX
CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
CONFIG_ARCH_WANT_FRAME_POINTERS
CONFIG_ARCH_WANT_HUGE_PMD_SHARE
CONFIG_CLONE_BACKWARDS
CONFIG_COMMON_CLK
CONFIG_EDAC_SUPPORT
CONFIG_GENERIC_ARCH_TOPOLOGY
CONFIG_GENERIC_ATOMIC64
CONFIG_GENERIC_CLOCKEVENTS
CONFIG_GENERIC_GETTIMEOFDAY
CONFIG_GENERIC_IOREMAP
CONFIG_GENERIC_IRQ_MULTI_HANDLER
CONFIG_GENERIC_IRQ_SHOW
CONFIG_GENERIC_PCI_IOMAP
CONFIG_GENERIC_PTDUMP
CONFIG_GENERIC_SCHED_CLOCK
CONFIG_GENERIC_SMP_IDLE_THREAD
CONFIG_GENERIC_STRNCPY_FROM_USER
CONFIG_GENERIC_STRNLEN_USER
CONFIG_GENERIC_TIME_VSYSCALL
CONFIG_HANDLE_DOMAIN_IRQ
CONFIG_HAVE_ARCH_AUDITSYSCALL
CONFIG_HAVE_ARCH_KASAN
CONFIG_HAVE_ARCH_KGDB
CONFIG_HAVE_ARCH_KGDB_QXFER_PKT
CONFIG_HAVE_ARCH_MMAP_RND_BITS
CONFIG_HAVE_ARCH_SECCOMP_FILTER
CONFIG_HAVE_ARCH_TRACEHOOK
CONFIG_HAVE_ASM_MODVERSIONS
CONFIG_HAVE_COPY_THREAD_TLS
CONFIG_HAVE_DMA_CONTIGUOUS
CONFIG_HAVE_EBPF_JIT
CONFIG_HAVE_FUTEX_CMPXCHG
CONFIG_HAVE_GENERIC_VDSO
CONFIG_HAVE_PCI
CONFIG_HAVE_PERF_EVENTS
CONFIG_HAVE_PERF_REGS
CONFIG_HAVE_PERF_USER_STACK_DUMP
CONFIG_HAVE_SYSCALL_TRACEPOINTS
CONFIG_IRQ_DOMAIN
CONFIG_MODULES_USE_ELF_RELA
CONFIG_MODULE_SECTIONS
CONFIG_OF
CONFIG_OF_EARLY_FLATTREE
CONFIG_OF_IRQ
CONFIG_PCI_DOMAINS_GENERIC
CONFIG_PCI_MSI
CONFIG_RISCV_INTC
CONFIG_RISCV_TIMER
CONFIG_SPARSEMEM_STATIC
CONFIG_SPARSE_IRQ
CONFIG_SYSCTL_EXCEPTION_TRACE
CONFIG_THREAD_INFO_IN_TASK

is selected by
CONFIG_CLINT_TIMER